This sounds like a joke that needs a punch line.
I've had ArcGIS for Server 10.4.1 running fine for many months, and yesterday all map services said "shutting down".
I got multiple errors in the server log with codes like 9999, 7701, 6550. I couldn't publish new services and it wasn't working even after the customary reboots, starting and stopping of services etc.
ESRI tech support determined that the local arcgis account no longer had full permission to access the entire ArcGIS directory and a few others that had been created during installation. I've changed permissions to add the local account privileges back in. This appears to have fixed things.
Has this happened to anyone else, and does any one know of a windows or other update that might cause this?