Are you able to post the workbook (twbx file) so that I can take a closer look?
I was experiencing the same issue and contacted Tableau Support. The fix was quite simple - the online maps were not turned on. Here is the response that I received and that worked for me:
During my initial troubleshooting steps, I noticed the menu option for Background Maps is set to None in the workbook provided. I believe this option may have been automatically selected by Tableau Desktop when My Tableau Repository was moved, as the product was unable to locate the map source file. I was able to show the map underneath the plotted points in the workbook provided by selecting the Online menu option for Background Maps by doing the following:
Navigate to the Map menu > Background Maps > Online