Corrupt File/Can't open - no backup?

Last saved version: aug 12, 19
Using: Excel 2011
Saved on: USB thumb drive
Using MAC, but have access to old laptop with windows.

Error I get: Excel cannot open the file 'filename.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." It usually indicates the file is not compatible with the Excel version or the file has come corrupt or damaged

We we reset our breaker the other day, I am guessing this might have caused this to happen.

Questions:I only have the most current version saved on my USB (cant open/get the error message). I had many formulas set up inside.
1. Does my USB create backups I cant see?
2. What are the odds of this being able to be opened at all, in any format?

Please help!

I know. I am so stupid! I can't believe I let myself do this without a recent backup saved. I did try to change to .XLS and I think everything showed up as Y's.

I would do almost anything to not have to go back and recreate this. Thank you for your response.

I have downloaded 2 without success. One of them is from a company that had me send the file to their lab, but I am not going put too much hope into as I have the feeling I am screwed. Thank you.

I dont want to post it public because it has sensitive financial information. I would rather have someone request the file to their email so that I can send.

"Excel cannot open the file 'filename.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." It usually indicates the file is not compatible with the Excel version or the file has come corrupt or damaged.