We have recently put our users on office 365 with E1 License. Users are having issues with excel files opening or being able to print. We received a .xls file and when you try to preview it outlook web app gives the error. "There is something in your workbook that we don't understand. Try opening and saving the workbook in a newer version of Excel.. Users only have access to the online apps and do not have excel on their desktops to be able to download an open in the desktop version of excel. I need a solution to this. There is no option to print so they can not save as a PDF.
I have even tried to save to One Drive and open from the excel app and I get the same message.