Apple TV App on Samsung cannot verify login. error message displays before allowing an attempt.

Sign In page goes to 'Verification Failed' before it even allows entry of user id or password. Tried 'Sign in on mobile device'. Tried 'Create Apple ID'. Both of those pop the error immediately before displaying a login form. 'Sign in on this TV' allows the entry of user id and password, but then displays same error. Tried 2 TV factory resets. Tried numerous Apple TV App resets. Tried cold shut down of TV, plus pull plug for 5 minutes. Nothing working. Same account works fine on other TV and mobile phone. Clearly App failure on this TV. Samsung QTQ60. Worked fine for a year then stopped working.