Keynote will not update on iPad - endless sign in loop
Running IOS 9.2 on an iPad air. Desktop is a 27" Retina iMac running OS 10.10.5.
I made a Keynote presentation that is about 700MB on the iMac and copied it to the iPad through iTunes. The presentation won't open because it says Keynote needs to be updated to the latest version. I go to the app store and try to update, it asks me for my Apple ID, I enter it, then click Update. The download circle starts to spin for a few seconds, then stops and it says "Update" again. When I try to do it, it asks for my ID again, and the whole cycle goes on infinitely.
Does anyone have any ideas? i have to give this presentation on Thursday and i am getting nervous about trusting the iPad to be able to do it.
iPad Air, iOS 8.1.3