Most likely your Excel.XLB toolbar customisation file is corrupted.
Do a search for *.XLB including hidden files and folders.

Rename the file and reopen Excel - you will lose any toolbar
customisations you had previously done. If that doesn't solve the
problem, delete the new XLB file and rename your old one back- and come
back for another suggestion

Bill Manville
MVP - Microsoft Excel, Oxford, England
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