My sons iTouch stopped being connected to messaging, icloud, FaceTime, etc. it asks us to log in but does not seem to process the password. We finally get the following error. The certificate for this server is invalid. You might be connecting to a server that is pretending to be "setupIcloud.com" which could put your confidential information at risk.
I have backed up his device on a computer and updated to the latest software and verified his password is correct logging in to his Apple ID on a computer.