Close all other workbook message

If when click on Upgrade button you get a dialogue saying “Please close all other workbooks” but you don’t have any other workbooks opened apart from Tabular.xlsm

This usually indicate that you have some hidden workbooks opened. Sometimes workbooks are open on starting Excel in order to execute a macro(registering a shortcut, etc..) and this workbooks are hidden. To close them do the following:
From Excel ribbon go to Tab View -> Unhide
If some workbooks show unhide them and close and you will be able to proceed with upgrade.