If anyone is trying to open an excel file ( that has changed to cpgz.xlsx ) on sonoma.

If your trying to open a Microsoft excel file on Sonoma and find it wont recognise or you end up with gobbledegook ( even after changing the opening app on get info).

The following solved the problem for me.

I fortunately have Catalina on an older imac and was able to open it on that with an older version of Excel version 16.66.1. Fortunately without the older imac it would have been a disaster for me as I have years of data on the Excel file I use frequently.