See if this helps,
Also what is your extract based on? A database? Excel file?
Thanks for your reply.
I'm not using excel file. I'm using Oracle and MySQL as my database.
The error is so generic that I'm not able to trace it.
I tried to recreate the report and publish it. The Extract refresh worked for first two times and then again I'm getting the same error message.
What has changed? Make sure Tableau Service account has proper permissions setup, and is your extract connected to both databases (MySQL and Oracle?) Is that a scheduled refresh extract? Could your try to run it manually and see if it's still failing?
You said you're unable to locate logs?
Here's typical location of logs in Tableau Server - C:\ProgramData\Tableau\Tableau Server\data\tabsvc\vizqlserver\Logs
All these are just trial and error, there could be many reasons hence It's difficult to troubleshoot without looking at logs. Have you opened a case with Tableau Support? I think that's your best bet.