Hello GH,
Can you perform the WSUS health check, i.e. make sure WSUS is working fine.
"C:\Program Files\Update Services\Tools\WsusUtil.exe" checkhealth and check the result in eventviewer. Please share the result. If WSUS is working fine. Please perform the SUSDB cleanup.
Is WSUS and SUP on same server? And check if WSUS pool is running or not.
Regards,
K