I received this question from Teresa H. in England today and fortunately, it ended with a very easy answer for her!
I have a macbook pro with the original PowerPoint for Mac. None of the keys work on the keyboard, if i insert a text box or word art I cannot type in those either. (I just updated to Mac OS X Yosemite).
The very first thing I told her to try was to simply do an update of the Microsoft Office suite by heading to the help menu and choosing “Check for Updates…” This was the answer to her issue, because when it finished its series of updates, the keys started working again. I received a follow-up message shortly thereafter:
Thanks Mark…that worked you’re a genius!
Always remember–when in doubt, perform your updates first!