WSUS 3.0 SP2 on SBS 2003 R2 - After reinstall of WSUS clients appear in console but none are reporting

After reinstalling WSUS (following procedure in Technet document 70809) I can see all computers have been detected and are displayed in the Update Services console but none have reported after several days. All clients were reporting before the reinstall.

I have run wuauclt.exe /resetauthorization /detectnow but this does not work.

I have checked the registry settings:

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\WindowsUpdate
     WUServer    REG_SZ    http://METSVR01:8530
     WUStatusServer    REG_SZ   http://METSVR01:8530
     ElevateNonAdmins    REG_DWORD    0x1
 HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\WindowsUpdate\AU

I have run client diagnostics:

Checking Machine State
        Checking for admin rights to run tool . . . . . . . . . PASS
        Automatic Updates Service is running. . . . . . . . . . PASS
        Background Intelligent Transfer Service is running. . . PASS
        Wuaueng.dll version 7.6.7600.256. . . . . . . . . . . . PASS
                This version is WSUS 2.0

Checking AU Settings
        AU Option is 3 : Notify Prior to Install. . . . . . . . PASS
                Option is from Policy settings

Checking Proxy Configuration
        Checking for winhttp local machine Proxy settings . . . PASS
                Winhttp local machine access type
                        <Direct Connection>
                Winhttp local machine Proxy. . . . . . . . . .  NONE
                Winhttp local machine ProxyBypass. . . . . . .  NONE
        Checking User IE Proxy settings . . . . . . . . . . . . PASS
                User IE Proxy. . . . . . . . . . . . . . . . .  NONE
                User IE ProxyByPass. . . . . . . . . . . . . .  NONE
                User IE AutoConfig URL Proxy . . . . . . . . .  NONE
                User IE AutoDetect
                AutoDetect not in use

Checking Connection to WSUS/SUS Server
                WUServer =http://METSVR01:8530
                WUStatusServer =http://METSVR01:8530
        UseWuServer is enabled. . . . . . . . . . . . . . . . . PASS
        Connection to server. . . . . . . . . . . . . . . . . . PASS
        SelfUpdate folder is present. . . . . . . . . . . . . . PASS
        SelfUpdate folder is present. . . . . . . . . . . . . . PASS

When I attempt to connect to http://metsvr01:8530 in a browser, I get:

The website declined to show this webpage
 HTTP 403 
 Most likely causes:
 This website requires you to log in.
 What you can try:
 Go back to the previous page.
 More information
 This error (HTTP 403 Forbidden) means that Internet Explorer was able to connect to the

website, but it does not have permission to view the webpage.

I suspect this is at least part of the problem but I don't know where to check for this.

If I open http://metsvr01/selfupdate/wuident.cab, I am prompted to open or save wuident.cab

I have looked at threads in this forum but can't see a solution.