You might not expect a WSUS blog post on a site maintained by an Exchange consultant, but there are still customers using Exchange servers on-premises, and these need to be patched as well (and so are the clients of course).

After installing and a new WSUS server running on Windows 2016 I quickly ran into an annoying issue after configuring the WSUS server and downloading the updates. The console would no longer connect and generated a ‘Connection Error’ popup saying “An error occurred trying to connect the WSUS server. This error can happen for a number of reasons. Check connectivity with the server. Please contact your network administrator if the problem persists.”

When you click the copy error to clipboard button the following is copied:

The WSUS administration console was unable to connect to the WSUS Server via the remote API.
Verify that the Update Services service, IIS and SQL are running on the server. If the problem persists, try restarting IIS, SQL, and the Update Services Service.
The WSUS administration console has encountered an unexpected error. This may be a transient error; try restarting the administration console. If this error persists, Try removing the persisted preferences for the console by deleting the wsus file under %appdata%\Microsoft\MMC\.

If IISRESET was executed, it runs again for some time, but then the issue happens again. When looking at the IIS console when this error occurs it turns out that the WsusPool was stopped as can be seen in the following screenshot:

Starting the WsusPool solves the problem temporarily, but after some time it stops again. And again… and again…

It turns out to be a private memory issue in the WsusPool which seems to be depleted quickly. It is possible to assign more memory, but since I have no clue how much memory to assign I changed the setting to ‘0’ (1,843,200 KB is default) so the WsusPool can use anything it needs.

After changing the private memory limit for the WsusPool the error no longer occurs.