iPhone can't connect to iCloud server
Hi!
My son's iPhone can't connect to the iCloud server. App Store is unavailable. In the iTunes and App Store pane of the Settings app I cannot log in. Reset of iPhone is not possible. Restore from iTunes on Mac is not possible, because Find My iPhone is active on iPhone, and it can't be turned off, because in the iCloud pane of the Settings app nothing can be done until I accept new terms and conditions, which can't be done.
Wifi on the phone works great with Safari, but Mail cannot get new emails. The Weather app does not connect.
His iPad which is logged into the same iCloud account has no problems, and there is no trouble logging into his account on iCloud.com.
I tried restarting and hard resetting iPhone, as well as updating to 9.3.4 via iTunes on Mac (which went painlessly but changed nothing).
Any help much appreciated!
iPhone 5s, iOS 9.3.1