Figured out that it was of the date calucations that the newer version didn't like. Redid the calculation and it's working now.
We are at the stage to spend time on upgrade Tableau server from 10.1 to 10.5 or the 2018.1 etc.
It would be really helpful if you could kindly let me know what is the calculation, and why the refresh failed and what is the fix.
Thank you so much!