Unable to load the old XLS file in Office 365

Hi, 

I am now working with some old files that were created in 97-2003 Worksheet.XSL files, which was updated recently by someone else. 

I am using office 365 to load these files. I have trouble loading the data into Excel. The files are opened in excel but I could not see any information. I cannot use "save as" to convert or save it in a better compatible format. 

I opened the files by two ways. "Double click on the file" and "Go from the open tab". Neither works. I also try to open them from "office365.com" . Do not work, either. Only blank excel sheet appears and no file name is displayed at the top. When I hit the "File" button, the tabs "info", "Save", "Save As", "Print", "Share", etc are faded and cannot use them. 

I have been spending on this problem a tremendous amount of time and still get stuck in it. I would appreciate if someone could help me solve the problem.