Have you checked if the Excel worksheet name is still the same. It may happen that the worksheet name changes and it will break all the connection.
If that isnt the case I suggest for this time to rebuild your data connection to restore your service and then monitor it until it gets stable again.
I hope this helps
Rodrigo Calloni - Yes, everything is same. Filename, headers
rebuilding is not an easy option. I have 30 worksheet inside tableau. But only one worksheet in excel.
maybe I can download that same excel from the temp folder I see, when I click on Edit Connection & then see what I get.
Maybe you could check the Desktop logs and see if the error there can give you any extra hint on the source of the problem.
You can also open a support case and Tableau the logs following these instructions on how to get a clean version: