Please mark the answer as CORRECT & HELPFUL if it helps you so that it can help others as well
This sort of helped. It gave some options that could correct the issue, but it doesn't tell you how to implement those changes in Tableau. The data sources for my workbook were already set to "run as account". This page gave instructions on how to modify settings on the SQL Server, but not in Tableau. I hesitate to make a modification on the SQL Server, because I don't want to cause problems for others who are not trying to access this particular workbook and use SQL Server on a daily basis. I found the setting for the workbook to access the data source using "impersonation", but I could not find where you could put in who/what you wanted to impersonate.