Solved! Go to Solution.
I would check if your SQL Server instance was switched to a different Server, or if any permissions were changed. You can check if you still have access by going to Start > ODBC Data Sources (64 bit) > Add > ODBC Driver 17 for SQL Server > Enter the correct credentials > Test. If the ODBC DSN doesn't work, it will spit out a clearer error code. If there's an error on the ODBC DSN, then it's not an Alteryx issue.