Logging into android classic app not working on some devices

I use the same log in to log into my cellphone and samsung tablet and everything is fine. Using the same log in to another tablet that I use for remote controlling that is mounted on the wall, and it is not working any more. I even went as far as trying to reset password and never get an email to do so. I have submitted a support ticket and got a response to contact classic smartthing, but there is not contact under classic. Seems there is no support period. Is this just me or is someone else having issues?

SmartThings or Samsung account? Have you tried to select New User when you login and then choose the appropriate account?

Smartthings app, and I am not a new user. I have been using this app for 4+ years. And I don’t have issues with the same log in on other devices, so why this one?

Is it an Amazon Fire Tablet? Have you recently Been migrated to a Samsung login?