Trying to patch one of my administrative servers and was receiving that error message. Server is 2016 standard, domain-joined, and there is WSUS in the environment along with the associated GPO’s for WSUS use.

Looks like this error is/was received due to the fact that my WSUS server was experiencing some issues.

• Log into WSUS
• Open IIS Manager
• Navigate to Server Name > Application Pools
• Find WsusPool
• Start (or restart) this pool

In my case the pool had stopped due to an issue encountered when running a WSUS cleanup script. Starting it and then re-running the update check (retry button), yielded much better results.