Herm.. I have not seen this particular error. The first thing I would do to troubleshoot this is select the target machine and right-click -> Computer Explorer. When that opens I’d go to the System Information tab; it uses a very generic WMI connection (that does not use our WMI Providers to get the info). So, if that tab works the basic connectivity is there.
Next I would try the Windows Update Settings tab next to that one. That does use the SolarWinds' WMI providers to pull data from the machine. If it throws an “Invalid Namespace” error, something is blocking the WMI Provider from talking or they aren’t installed (typically). If that tab does retrieve and display data, the WMI Providers are good to go.
The error itself is implying that the client machine can’t pull the update down from WSUS. With an Update Management task, Patch Manager is making a WMI connection to the WMI Providers on the target machine, and through that it is telling Windows Update Agent on the target machine to go pull the specified update(s) down from WSUS and install them. So, on that Computer Explorer window I’d also check out the Windows Update Settings tab to make sure it is pointed to the right WSUS server on the right port. That would be the "Intranet WSUS Server Service Connection" field.
Just checking the most obvious things here, but sometimes those are the ones that get ya.
Thanks for that info. It turns out that the intune client that we had installed on the machines was causing the problem. Not sure why...