A family of Microsoft word processing software products for creating web, email, and print documents.
I had this same issue - tried everything suggested in this post - with no succes. However, after contacting Microsoft Support, I was able to find a solution:
Log out of word (make sure it shows you are logged out in the top right corner (there should be a "sign in" button instead of your name). Close word.
Open "File Explorer" --> In the bar above "Quick access" choose "View" and then select "Show" and then "Hidden Items" --> Find the (C:) drive (under "This PC") --> Users --> Then choose the folder corresponding with your username --> AppData --> Local --> Microsoft --> OneAuth --> In the OneAuth folder delete the folders "accounts" and "blobs" --> Navigate back to the "Microsoft" folder from earlier --> Delete the folder "Identity Cache" --> Restart word and try to log in.
Hopefully this works - it helped me after everything mentioned here failed to solve the issue.