What:
When using the Excel Plugin connecting to AzureDevOps to bulk maintenance of backlogs, sometimes your cache can be corrupted.
The Plugin can connect and see the server(s) and your queries from AzureDevOps.
But it crashes when you try to load the query.
The solution is to delete the cache.
How:
On windows navigate to the locations and delete the cache files:
%LOCALAPPDATA%\Temp\Microsoft\Team Foundation\x.0\Cache
:\Users\"UserName"\AppData\Local\Temp\Microsoft\Team Foundation\9.0\Cache