A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
It seems there are many things that can cause symptoms similar to what everyone is experiencing in this thread, but here's what fixed the grey "blank" screen for me. The workbook was simply hidden.
If your screen looks like this after opening your file:
Go to the View ribbon, and click "Unhide". You'll be asked which workbook to unhide, if you only have the one file open, click Yes.
This hidden state is saved along with the file, so it might sometimes seem that the file is corrupt, because it will be hidden on any computer you try it on.
Hope this helps someone, and sorry if this answer had been provided already, I did try to scan through previous posts.