RE: excel cannot open the file .xlsx because the file format or file extension is not valid. verify that the file has not been corrupted and that the file extension matches the format of the file.
I work for a very large corporation that licenses the POS Office 365. Why POS? Simple, Excel crashes from time to time, sometimes repeatedly after updates. Features are missing that I use at home on my Office 2010 system, and lastly, cloud based computing is insecure, slow, and subject to network issues. They maintain thousands of systems world-wide remotely, and maintain high security settings as well as security software. Reinstalling Office 365 is not an option for me as only a remote IT person can do so. Local, files on my computer open, the file I've lost access to is on a networked drive.
I was working on a file yesterday that I've spent many weeks on, saving continually as I work, and then saved and closed Excel at the end of the day. This morning, Excel launched fine, but I got the error message "Excel cannot open the file blahblah.xlsx because the file format or the file extension is not valid. Verify that the file has not been corrupted and that the file extension matches the format of the file".
I've tried opening Excel in Safe Mode, and that doesn't help. I've copied the file and tried to open it at home, and get the same error message. I searched the internet for solutions, finding many unrelated resolutions; rename the file and changing the extension to xls, changing the Trust Center settings, etcetera, all to no avail.
I'm hoping someone has the real answer.
thanks