Over the Datto web portal, on the Protect tab, if one of the servers has a screenshot failure, and when you click on the screenshot it shows a Windows Update screen, this means that the system was running the Windows update by the time the Datto took that specific backup that was used for the test.
In this case to resolve the error, just make sure to reboot when it’s possible the physical server in question, and on the next backup and screenshot test this should be cleared automatically.