was this all of a sudden or after an update? if rebooting the phone does not work then you might have to do a factory reset. if you do keep in mind that this will trip FRP (factory reset protection) and you will need your google acct info......so make sure you know your email and password you used when first setting the phone up. otherwise you will be locked out of the phone.
also keep in mind that you will lose data as well so make sure that you use Smart Switch to back everything up.[/QUOTE
happened after a factory reset