Office 365 University - I already have it working and activated, but recently it is asking for activation every time I try to use it!!!

Whenever I open Office on my windows 8.1 computer I get a request for activation.  When I try to activate it it will give me an error.  If I try and click on "enter product key instead" it goes into a small window that says its setting up office for me, but it just perpetually stays in this mode.  I then have to use task manager to get out of the program! (end task).  I need solution asap!