Today having problems with an Excel file on a Windows 7 laptop. I worked with this file last night without any problems. The file was saved on a network drive and during saving have not been received error.
When this morning I needed to open the file I got the message about error. "Excel cannot open the file because the file format or file extension is not valid". And also the file is showing up as having 0 KB.
I tried an Excel repair on the file and also opening up in another program like .docx or .txt. Is there any way of finding out what happened this file or fixing the issue.
File server is running Windows 2012 R2 Server. Shadow copies are available and I can restore the file to previous version; however, the user did a lot of work after that time.