For a high priority issue like this, I'd certainly recommend contacting Tableau Support. It's the most reliable way to resolution for a server down situation.
If you do want to pursue the issue here, please include some information about the issue. Screenshots or snippets from logs are most useful. Anything that will help to identify the issue.
I suggest you check any automated scripts on the server which run daily that which might be changing something and thereby causing this issue.
Also check the logs to find what is happening.