I have two copies of the spreadsheet for my research project on my MacBook Pro; one cannot be opened and displays "Excel cannot open the file '~$PLT Data Sheet.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." when I try to open it, and the other opens but doesn't have any of the edits that I've made in the last month. Additionally, autosave says "this file location doesn't support autosave", so I don't know what to do to try to recover my hours upon hours of work :(

I also cannot figure out how to attach those files to this post :( I am so bad at this

Any help would be greatly appreciated!
I am running Excel 16.18, and my MacBook is a year old.