Office Errors
There are several errors that can happen when someone attempts to open an Office application. This article will try and break those down with solutions.
License Issue
Windows
On a Windows machine the fix would be to clear the cached credentials from the system. Instructiosn with step-by-step pictures can be found here.
Mac
On a Mac, there is an app you can download which will go through and wipe any cached credentials out, allowing you then to sign in with the one you need and get you back to working order. The article for more details is here.