Hi, we have an issue that's occured on one of our ePO servers, when we log in we get "this monitor cannot be opened due to an unrecoverable error" on nearly all of our dashboards. I found an archived article that suggested this was due to the install drive being full and indeed we believe this may have been the case for us, however, we now have plenty of capacity back (around 5gb) and have rebooted the ePO server but we still cannot load any of the dashboards.
The most common reason I've seen for that issue is that the extension that provides that dashboard element has been removed. Other than that go into queries and see if you can run the report manually. If you cannot run it outside of the dashboard then it won't work in the dashboard either.