iMessage & Facetime stopped working??

I have two devices that were sharing the same iMessage email.... It was working just fine for both, but then out of nowhere one of these devices told me that i have to sign in or sign up? So i signed in, and then it told me that i need click on an email to use with it. The email availible was the right one, but for some reason it is greyed out so i cant click on it. The iMessage now only works with one of the devices. The FaceTime will not work on either device. Can these two apps work on 2 devices? Help me please!