Error message when activating Office 365 for mac

Try again in a few hours. Could have an issue with the Login Server.

Or you could have Bad Install.

Microsoft has published a set of directions to Remove all Trace of 2016 install.  Note : This is what is called a "ScorchedEarth"  removal.

Remove Office 2016 

You might get By with doing this instead:

1. Open Applications Folder, either by opening:
   From Dock — click Applications icon in Dock hold Mouse right button down or, control Key - left button.
   
   A Context menu appears. Click Options and choose Open in finder.
   Locate all  Office 2016 applications.
   
   (Or, open Hard Drive locate Applications folder. Locate the Office 2016 applications.
   
   
   
2. Remove all of the Office 2016 applications they will be listed separately:
   Excel
   OneNote
   OutLook
   PowerPoint
   Word
   
   Move them to Trash at this time. (But do not empty Trash at this time.)
   
   Next go to Finder, Hold down Option Key and click on GO Menu.
   
   Click on Library.
   
   Open Preferences open Containers Folder.
   Now look for and Remove any Container Folders that have Office, Word, Excel, PowerPoint and possibly (if there is any for) OutLook and OneNote. Remove those to Trash(But do not empty yet).
   
   
   
3. Now go back to your Account Page for 365 (sign  in) and re-download Office 365 and re-install.
   
   
   
4. Now Open one of the Office 365 applications (OneNote or Word will be ok).
   
   
   
5. If Connection is Good now try using procedure as before. And this time see if you go to a screen where it ask for Username/Email Address and Password.  Be sure to use exact Email address and password used to purchase.
   
   
   
6. If successful, you should be greeted with a screen on your web Browser that has similar details as this: (note; I blocked out section with possible personal info from view here, if you have Sharing setup)
   
   
   
   
7. Leave your browser open and click Visit Skype.
   Sign in using same Credentials used to buy Office 365. Then you click on 60 Free Minutes.
   After collection of Minutes, sign out.
   
   
   Go back to the Account page, and this time click visit OneDrive
   (sign in using same ID and Password used to purchase 365).
   
   
   You might see a Screen that says congratulation You now have 1TB space available or something similar. When finished, sign out.
   
   Go back to Account page and Bookmark
   (You will need to go back from time to time.)
   (If you pay month to month, you might have visit to visit once a month to sign in.)

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Disclaimer:

The questions, discussions, opinions, replies & answers I create, are solely mine and mine alone, and do not reflect upon my position as a Community Moderator.

Thanks Phillip.

I will try uninstall/install suggestion although uninstall is painful!!

Regarding:

"If Connection is Good now try using procedure as before. And this time see if go to a screen where it ask for Username/Email Address and Password."

In fact, this screen appear every time but then shows the error message.

The mistake I did, and hope others will not, is that I uninstalled office 2011 :(