I recently rebuilt my WSUS/SUP server and after running a sync, was presented with a sea of red giving me an error for each and every update it tried to sync.
Transpires this is a result of the (relatively) recent enforced strengthening of the TLS protocol by Microsoft. The fix is pretty simple though. Jump onto your WSUS server and just run the commandline below to configure .NET Framework to support strong cryptography:
reg add HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\.NETFramework\v4.0.30319 /V SchUseStrongCrypto /T REG_DWORD /D 1
Now resync your updates and all should be well.
I also ran into an issue after this whereby the wsyncmgr.log ‘synchronized’ all the updates (well appeared to do so) but no meta data appeared in the console. To fix this I unchecked all products and categories, sync’d again, then rechecked those I needed. I ran the sync once again and they all appeared.