I had the same issues with Office / Word 2016 fro Mac. Asking for permissions when trying to open a file, whether the document it was saved on the server or desktop, using Yosemite.
After many hours of trouble shooting and going in circles, I went back to basics and found that I had no problems opening word docs when:
- Starting in safe mode
- Creating a new Admin User
Both of these methods do not install 3rd party apps, which confirmed it was likely to be font related as font management software (Suitcase) is not installed in either of the above.
I Deactivated all the fonts in Suitcase (except those in system folder), cleaned my font cache, and checked for corrupted fonts.
Restarted my computer.
I was able to open Word docs.
I then Activated on all my fonts in Suitcase (1500+ fonts) and Word still works fine.
To me it seems, there is a conflict with 3rd party font management and word needs to open and load its required fonts first.
I have added Word to load at start up in System Preferences: User : Login Items.
Then load Suitcase and Activate fonts.
If you Quit Word, you will need to Deactivate the fonts in Suitcase , Start Word, then Activate fonts in Suitcase.
Good luck and if anyone from Microsoft or Suitcase/Font Management sees this .... please find a fix !!