Hi,
Did you get any error messages when you try to save Office documents?
Have you ever installed Office for Mac 2011 in your Mac?
In addition, I have done some research and find someone encountered the same issue and he resolved the issue by a clean uninstall/reinstall of Office. Would you try this to see the outcome? For your reference:
Troubleshoot Office 2016 for Mac issues by completely
uninstalling before you reinstall
Please try this method first and let me know the result, I'm glad to help you.
Regards,
Emi Zhang
TechNet Community Support
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