Data Model Error - Effecting all versions of the same workbook

[Rollnation3]

When I try to save or modify a pivot table in an open workbook, I keep getting this error message "An issue with the Data Model is preventing Microsoft Excel from opening this workbook. Try restarting Microsoft Excel".
I have tried previous versions of the same template that have always worked perfectly and get the same error.

It happened the day after duplicated the simple pivot table - a VERY simple data model that performs a distinct count of names in a data set. I then sent the workbook to a colleague via email.
Ever since I duplicated the pivot table I cannot refresh or work in the workbook without getting this error. This is happening throughout all versions of the same workbook.

Also tried to delete the pivot table and recreate it and still receive the same error.
I re-installed excel and still get the error.

I am using Excel 2016 professional plus, researching answers on the internet provide solutions for newer versions.
Any advice would be extremely valuable!

Thanks!