Did you change your password and not getting reflected in the Tableau side might get this error.
No I have not changed the password.
All the data are being pulled properly from other rows and columns.
Only this dimension "ActionMessage" is causing the error.
I hope that clarifies the question.
When you get the "error occurred" message, press "Show Details" and include those as well.
Does the query you list in "Query in the Background" work if you run it directly using SQL Server Management Studio or any other SQL Server tool?
My guess with too little information is that the ActionMessage column is a binary (blob) column of some kind in MySQL but mistakenly reported as a string to Tableau by SQL Server. When Tableau generates a "GROUP BY" on this column, MySQL rejects the query.