I updated to the 6.3.41 firmware. Since then, I get this answer if I want to log in: Failed to add account. Try again. First i fixed the “This device is not Play Protect certified” error. I enter the account name, then the password, but I always get this message. There has also been a restart twice. Moreover, the factory reset as well. Of course, the datas are correct. I don't understand.
Now another FR, another ID number registration, same problem I can't belive it! The YT login works, but the Google account login failed.
After FR the cookies are cleared to. But unbelievable, passed the second login attempt after the third FR. I don't understand what happened. I hope not all firmware update like such!