Can't open a SharePoint file in Word Mac 2016

Hi guys, 

 

The title of this post looks similar to an existing problem that happened in the past but I didn't find anything like this here. There is the reason for posting!  

 

While I am trying to open a file from SharePoint to edit in Word (not in the browser), a window pops up with an old username that I used to have and then all the time I have to try to sign in with a different account but after doing that I am getting an error message. 

 

Here is the first screenshot when the application requests the sign in option. 

 

Here is the second screenshot of an error message that comes up after trying to sign in with the right account. In the beginning, the error message had a different content saying that there was an error trying to establish the connection to the server.  

 

Does anyone know how to fix this problem? I have tried to remove the application, delete the cache, and different things like updating the office but I got no luck. 

 

Thank you!