Cannot open spreadsheets

Overnight I find it impossible to open two of my most important spread sheets. I have tried 'File > Open', double click the file, etc but they do not open. I can open any of my many other files with no trouble. When I 'Get info' the ones that open have identical properties to those that do not open. Also in the 'Get open' screen it says it was last opened when I last tried it but the file was never visible. I have searched the help file to no avail.

Suggestions please
Thank you

poppi

UPDATE-It appears I have solved my problems. Searching the internet I found a suggestion that I update my Excel 11.6.1 to 11.6.6 (had to do each of the 5 updates in sequence) but I can now open those two mysterious files in the normal manner. I have no idea why this worked but I am happy that it did

poppi