Entering icloud credentials on iphone closes the settings app

Hi - somehow my icloud account was removed from my iphonee 6+. When I try to add it back via settings>icloud, after i enter the logon and password the settings app fails.

I know the logon/password is correct, when I enter an incorrect password i am notified of this vs. when i enter the correct password, it closes the settings app. I can also access icloud through other devices using this same logon so the icloud account exists.

Any idea how to fix this?

Thanks!

- scott -