I had a problem with my samsung this morning. It locked up so I shut it down and restarted it only to be given just one option...... To 'reset' the phone.
I took that option and now I'm in the start-up mode and can't get past the Google login. I've enterered my gmail and password and it comes up with the following error message.
"Unable to sign into device due to unkown error. Please try another account or try to sign in again in 24 hours"
Because of this i can't get any further on the device so I'm stuck.
Sadly I have no answer but can sympathise as I've been getting the same with my Google Mini. I'll keep trying and if I crack it will be back to help you!