One thing to try would be to make sure that the native data source driver is installed on the Server machine. Then, restart Tableau Server.
If this still does not work, I'd recommend sending the issue into our support team, making sure to include Server logs and the packaged workbook (if possible):
Dear tracyfitzgerald ,
I tried even after installing ms sql server driver and reinstalled thrice tableau completely same problem exists. Any further guidance regarding this....Kindly mentioned the support team contact or where to get in touch with support team.
Thanks & BR,