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Dear Jonh,
Thanks for your updates.
Do you click on Command to select all sheets? Can you see the Ungroup option like the following?
If you do a test with a new Excel file, what's the result?
In some situations, some issues may be related to the version number of the Excel for Mac application. Keeping the version number latest is a good way preventing some issues at work. It seems that the version number of Excel for Mac you are using is a little old. If it is convenient, I suggest you update the version number, restart the Mac and then do a test to see the result.
Update history for Office for Mac - Office release notes | Microsoft Learn
Thank you for your effort and time.
Sincerely
Cliff | Microsoft Community Moderator