Pretty much all there is to it. Recently got office365 and it's been nothing but trouble, poor integration with my windows phone and now i can't even open my files. Excel 2013 (desktop) is useless to me because it can't open an excel sheet I want to work on. It's only 7.5 mb in size.
It can open previous versions of the file but the latest version of my sheet i'm working on refuses to open. I have no idea why this could be.