Error connecting to Apple ID server after updating iPhone 6 to iOS 10.3.1

Need help connecting iPhone 6 to Apple ID server.

Updated to iOS 10.3.1 and install seemed fine. Couldn't connect to Apple ID server at start up so skipped it to continue set up.

Then went into settings, entered Apple ID, says Verification Failed, error connecting to Apple ID server.

My Apple ID and password are correct.

My caps lock button is NOT on.

There is plenty of memory space on my phone.

Turn phone off/on, doesn't resolve.

Hard re-set, doesn't resolve.

Can't restore to prior iOS from iTunes because iTunes thinks i'm still signed in to find my iPhone even though i'm not because I can't connect to the Apple ID server. I can't log in/out of 'find my iPhone'- get the same verification fail error.

Also wants me to accept New Terms and Conditions but I think I have to be signed in first.

Feels like i'm stuck in a loop: have to sign in to accept terms but have to accept terms to be able to sign in.

HELP!!!!