Hi there, you might want to also contact Support and submit a case: Support Case | Tableau Software
The community consists of customer volunteers, and while you may not get a response here from other customers, Support is dedicated to troubleshooting errors.
Best wishes with Tableau as you move forward!
For this kind of generic error, you'll have to look at the VizPortal logs on the server. This is the fastest way to understand what went wrong.
As a first step, I would check you have provided the right username and password to connect to your database though.
Hope this helps,