MS 365 CoPilot Subscription

CowboyFive7 96 Reputation points
2025-02-02T05:15:31.7333333+00:00

I have a MS365 subscription and have had it for years. I added my wife's computer when I found out you can have multiple devices on one subscription. So, I went to her computer and logged into my account, downloaded MS365 app to her laptop and all was well. However, when I opened her Excel, I received the following error message "Excel cannot open the file "Book 1.xlsx because the file format or file extension is not valid. Verify that the file has not been corrupted and that the file extension matches the format of the file." I went back to my laptop and got the same error, which I have never seen before. After running in circles on various MS Help websites for days, and trying all they suggested, I come here for an actual straight answer. I am on "Book 14" now with no end in sight. My solution so far, as I need the program, is to "X" out of the error window and File-Open-New to a new spreadsheet which works fine. I can also open any of my old Excel files after I "X" out of the error window. Can anyone really, really help? Thank you, tons, in advance. The program works fine, it's just annoying and I wonder how large the "Book Count" will eventually get. Please help!

Microsoft 365
Microsoft 365
Formerly Office 365, is a line of subscription services offered by Microsoft which adds to and includes the Microsoft Office product line.
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