Windows Server 2016 not reporting to WSUS

I have an offline Windows Server 2016 WSUS server patched to the current February 2019 SSU and CU.  It has a set of approved updates on it for Windows Server 2016.

None of my Windows Server 2016 clients are reporting to it, however they are able to check and download updates without issue.  The client on the WSUS server can't report to itself either.

WSUS server and statistics location is set via GPO to http://FQDN:8530. Automatic update mode is set to 3.  Registry values are confirmed to be set by the GPO.  The Windows Update diagnostic tool has been run against both server and clients without effect.  I have rebooted both server and clients without effect.

I have tried manual scan: usoclient refreshsettings startscan

I have tried manual reporting: wuauclt /reportnow

I have tried manually stopping wuauserv and clearing out the SoftwareDistribution folder.

Nothing I have done makes any difference.  I cannot work out why the clients won't check in.

Examination of the WindowsUpdate log shows that the "Report" component on the client never logs anything:

2019/03/08 03:30:24.5819798 940   1092  Shared          * START * Service startup
2019/03/08 03:30:24.6036711 940   1092  Agent           WU client version 10.0.14393.2608
2019/03/08 03:30:24.6039172 940   1092  Agent           SleepStudyTracker: Machine is non-AOAC. Sleep study tracker disabled.
2019/03/08 03:30:24.6040146 940   1092  Agent           Base directory: C:\windows\SoftwareDistribution
2019/03/08 03:30:24.6044155 940   1092  Agent           Datastore directory: C:\windows\SoftwareDistribution\DataStore\DataStore.edb
2019/03/08 03:30:24.6230313 940   1092  Shared          UpdateNetworkState Ipv6, cNetworkInterfaces = 0.
2019/03/08 03:30:24.6230516 940   1092  Shared          UpdateNetworkState Ipv4, cNetworkInterfaces = 1.
2019/03/08 03:30:24.6234764 940   1092  Shared          Network state: Connected
2019/03/08 03:30:24.6256422 940   1092  Misc            LoadHistoryEventFromRegistry completed, hr = 8024000C
2019/03/08 03:30:24.6268401 940   1092  Shared          UpdateNetworkState Ipv6, cNetworkInterfaces = 0.
2019/03/08 03:30:24.6268469 940   1092  Shared          UpdateNetworkState Ipv4, cNetworkInterfaces = 1.
2019/03/08 03:30:24.6268528 940   1092  Shared          Power status changed
2019/03/08 03:30:24.6298602 940   1092  Agent           Initializing global settings cache
2019/03/08 03:30:24.6298612 940   1092  Agent           WSUS server: http://updates.REDACTED:8530
2019/03/08 03:30:24.6298619 940   1092  Agent           WSUS status server: http://updates.REDACTED:8530
2019/03/08 03:30:24.6298625 940   1092  Agent           Alternate Download Server: NULL
2019/03/08 03:30:24.6298632 940   1092  Agent           Fill Empty Content Urls: No
2019/03/08 03:30:24.6298638 940   1092  Agent           Target group: (Unassigned Computers)
2019/03/08 03:30:24.6298645 940   1092  Agent           Windows Update access disabled: No
2019/03/08 03:30:24.6302243 940   1092  Agent               Timer: 29A863E7-8609-4D1E-B7CD-5668F857F1DB, Expires 2019-03-08 04:31:32, not idle-only, not network-only
2019/03/08 03:30:24.6324420 940   1092  Agent           Initializing Windows Update Agent
2019/03/08 03:30:24.6325035 940   1092  DownloadManager Download manager restoring 0 downloads
2019/03/08 03:30:24.6325431 940   1092  Agent           CPersistentTimeoutScheduler | GetTimer, returned hr = 0x00000000
2019/03/08 03:30:24.6336617 940   3372  Shared          Effective power state: AC
2019/03/08 03:30:24.6336627 940   3372  DownloadManager Power state change detected. Source now: AC
2019/03/08 03:30:43.6510824 940   664   ComApi          * START *   Init Search ClientId = UpdateOrchestrator
2019/03/08 03:30:43.6510859 940   664   ComApi          * START *   Search ClientId = UpdateOrchestrator
2019/03/08 03:30:43.7129808 940   664   Agent           * START * Queueing Finding updates [CallerId = UpdateOrchestrator  Id = 1]
2019/03/08 03:30:43.7129860 940   664   Agent           Added service 00000000-0000-0000-0000-000000000000 to sequential scan list
2019/03/08 03:30:43.7130257 940   664   ComApi          Search ClientId = UpdateOrchestrator
2019/03/08 03:30:43.7181437 940   4928  Agent           * END * Queueing Finding updates [CallerId = UpdateOrchestrator  Id = 1]
2019/03/08 03:30:43.7228157 940   4928  Agent           * START * Finding updates CallerId = UpdateOrchestrator  Id = 1
2019/03/08 03:30:43.7228173 940   4928  Agent           Online = Yes; AllowCachedResults = No; Ignore download priority = No
2019/03/08 03:30:43.7228183 940   4928  Agent           Criteria = IsInstalled=0 and DeploymentAction='Installation' or IsPresent=1 and DeploymentAction='Uninstallation' or IsInstalled=1 and DeploymentAction='Installation' and RebootRequired=1 or IsInstalled=0 and DeploymentAction='Uninstallation' and RebootRequired=1""
2019/03/08 03:30:43.7228215 940   4928  Agent           ServiceID = {00000000-0000-0000-0000-000000000000} Third party service
2019/03/08 03:30:43.7228221 940   4928  Agent           Search Scope = {Machine}
2019/03/08 03:30:43.7228252 940   4928  Agent           Caller SID for Applicability: S-1-5-21-3731600443-1732068735-1633618523-500
2019/03/08 03:30:43.7228260 940   4928  Agent           ProcessDriverDeferrals is set
2019/03/08 03:30:43.7228265 940   4928  Agent           RegisterService is set
2019/03/08 03:30:43.7259109 940   4928  Misc            EP: error: 0x8024500C : - failed to get SLS data
2019/03/08 03:30:43.7259119 940   4928  Misc            EP: error: 0x8024500C: GetSecondaryServicesEnabledState failed
2019/03/08 03:30:43.7259151 940   4928  Agent           AutoRecovery: DetectAndToggleServiceState failed 0x8024500c
2019/03/08 03:30:43.7291641 940   4928  Misc            Got WSUS Client/Server URL: http://updates.REDACTED:8530/ClientWebService/client.asmx""
2019/03/08 03:30:43.9371533 940   4928  ProtocolTalker  ServiceId = {3DA21691-E39D-4DA6-8A4B-B43877BCB1B7}, Server URL = http://updates.REDACTED:8530/ClientWebService/client.asmx
2019/03/08 03:30:43.9373102 940   4928  ProtocolTalker  OK to reuse existing configuration
2019/03/08 03:30:43.9373142 940   4928  ProtocolTalker  Existing cookie is valid, just use it
2019/03/08 03:30:43.9373279 940   4928  ProtocolTalker  PTInfo: Server requested registration
2019/03/08 03:30:44.5053826 940   4928  WebServices     Auto proxy settings for this web service call.
2019/03/08 03:30:44.5278535 940   4928  ProtocolTalker  PTInfo: syncing with server using normal query
2019/03/08 03:30:44.5337456 940   4928  ProtocolTalker  SyncUpdates round trips: 2
2019/03/08 03:30:45.5174394 940   4928  ProtocolTalker  ServiceId = {3DA21691-E39D-4DA6-8A4B-B43877BCB1B7}, Server URL = http://updates.REDACTED:8530/ClientWebService/client.asmx
2019/03/08 03:30:45.5174410 940   4928  ProtocolTalker  OK to reuse existing configuration
2019/03/08 03:30:45.5174442 940   4928  ProtocolTalker  Existing cookie is valid, just use it
2019/03/08 03:30:45.5174455 940   4928  ProtocolTalker  PTInfo: Server requested registration
2019/03/08 03:30:45.6010503 940   4928  Agent           Policy driven service does not support additional filtering on feature updates.
2019/03/08 03:30:45.6010537 940   4928  Agent           Found 0 updates and 84 categories in search; evaluated appl. rules of 442 out of 736 deployed entities
2019/03/08 03:30:45.6228588 940   4928  Agent           * END * Finding updates CallerId = UpdateOrchestrator  Id = 1
2019/03/08 03:30:45.6234951 940   3088  ComApi          *RESUMED* Search ClientId = UpdateOrchestrator
2019/03/08 03:30:45.6239361 940   3088  ComApi          Updates found = 0
2019/03/08 03:30:45.6239370 940   3088  ComApi          * END *   Search ClientId = UpdateOrchestrator
2019/03/08 03:30:45.6248565 940   664   ComApi          ISusInternal:: DisconnectCall failed, hr=8024000C
2019/03/08 03:35:32.4174453 940   784   ComApi          * START *   Init Search ClientId = UpdateOrchestrator
2019/03/08 03:35:32.4174517 940   784   ComApi          * START *   Search ClientId = UpdateOrchestrator
2019/03/08 03:35:32.4348552 940   784   Agent           * START * Queueing Finding updates [CallerId = UpdateOrchestrator  Id = 2]
2019/03/08 03:35:32.4348596 940   784   Agent           Removing service 00000000-0000-0000-0000-000000000000 from sequential scan list
2019/03/08 03:35:32.4348627 940   784   Agent           Added service 00000000-0000-0000-0000-000000000000 to sequential scan list
2019/03/08 03:35:32.4348905 940   784   ComApi          Search ClientId = UpdateOrchestrator
2019/03/08 03:35:32.4395500 940   1956  Agent           * END * Queueing Finding updates [CallerId = UpdateOrchestrator  Id = 2]
2019/03/08 03:35:32.4441996 940   1956  Agent           * START * Finding updates CallerId = UpdateOrchestrator  Id = 2
2019/03/08 03:35:32.4442009 940   1956  Agent           Online = Yes; AllowCachedResults = No; Ignore download priority = No
2019/03/08 03:35:32.4442021 940   1956  Agent           Criteria = IsInstalled=0 and DeploymentAction='Installation' or IsPresent=1 and DeploymentAction='Uninstallation' or IsInstalled=1 and DeploymentAction='Installation' and RebootRequired=1 or IsInstalled=0 and DeploymentAction='Uninstallation' and RebootRequired=1""
2019/03/08 03:35:32.4442054 940   1956  Agent           ServiceID = {00000000-0000-0000-0000-000000000000} Third party service
2019/03/08 03:35:32.4442061 940   1956  Agent           Search Scope = {Machine}
2019/03/08 03:35:32.4442092 940   1956  Agent           Caller SID for Applicability: S-1-5-21-3731600443-1732068735-1633618523-500
2019/03/08 03:35:32.4442099 940   1956  Agent           ProcessDriverDeferrals is set
2019/03/08 03:35:32.4442104 940   1956  Agent           RegisterService is set
2019/03/08 03:35:32.4470435 940   1956  Misc            EP: error: 0x8024500C : - failed to get SLS data
2019/03/08 03:35:32.4470444 940   1956  Misc            EP: error: 0x8024500C: GetSecondaryServicesEnabledState failed
2019/03/08 03:35:32.4470473 940   1956  Agent           AutoRecovery: DetectAndToggleServiceState failed 0x8024500c
2019/03/08 03:35:32.4501433 940   1956  Misc            Got WSUS Client/Server URL: http://updates.REDACTED:8530/ClientWebService/client.asmx""
2019/03/08 03:35:32.6071937 940   1956  ProtocolTalker  ServiceId = {3DA21691-E39D-4DA6-8A4B-B43877BCB1B7}, Server URL = http://updates.REDACTED:8530/ClientWebService/client.asmx
2019/03/08 03:35:32.6073465 940   1956  ProtocolTalker  OK to reuse existing configuration
2019/03/08 03:35:32.6073547 940   1956  ProtocolTalker  OK to reuse existing configuration
2019/03/08 03:35:32.6073801 940   1956  Misc            Got WSUS SimpleTargeting URL: http://updates.REDACTED:8530""
2019/03/08 03:35:32.6075945 940   1956  ProtocolTalker  Initializing simple targeting cookie, clientId = 263f9e73-42ab-4b7a-adf3-9590311f3c77, target group = <NULL>, DNS name = ednsbar001.REDACTED
2019/03/08 03:35:32.6075957 940   1956  ProtocolTalker    Server URL = http://updates.REDACTED:8530/SimpleAuthWebService/SimpleAuth.asmx