Our Sony TV runs Android TV.
I recently went into the YouTube app and it said I was not logged in. I clicked log in and nothing. It just for around in circles telling me I'm not logged in and yet not allowing me a screen to log in on.
I removed my Google account and then re entered that but to no avail.
Under settings, it also says Sync for the Google account is unavailable and will be available shortly,although it has said that for a month.