especially important file.xlsx

Hello,

After a power outage, a particularly important file does not open, the error "Excel cannot open file.xlsx is due to the file format or the file extension is not valid. Check that the file has not been corrupted and that the file extension matches the file format. The file format has not changed. Is there a safe program that might not mess up the file? I tried to open and repair the file by changing the format using Open Office. Also tried using recova but the file was not restored.