I have this same problem, with a twist. It all started after I set up my new Mac Studio. The Excel file performs perfectly fine on my new Mac Studio (M2 Max, 2023). But when I copy it over to my MacBook Pro 13" (2019, i5 CPU) I always get this Error Popup on the MBP:
"Excel cannot open the file 'homeaccess.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."
Both systems are on the same MacOS, latest version (Sonoma, 14.5). The kicker is that this Excel file is password protected in Excel because it holds around 350 different WWW logon passwords. And yes, this Excel file password is known and hasn't ever changed. I can open the file with the password on the Mac Studio. But I always get the same Lock-Out error on the 2019 Intel MBP.
Is this perhaps a Microsoft security "feature" that saves the locked file within the .XLSX file, with an Apple Silicon-specific security key, which does not function properly on the Intel-based MBP? This Seems Plausible.
Another theory is that while both the Mac Studio and the MBP have encrypted file systems running, the MacOS (Apple Silicon) is applying a security key that is not accepted on the MBP's encrypted file system for some reason? (Perhaps because an M2-specific security key is not installed in the MBP because it does not have Apple Silicon???)
If you have any insights into this error (or perhaps just complexity), you would be a Life Saver, due to the nature of the file's contents locking my life out, while I'm on the road away from my home office and my brand new Mac Studio.