Help! Why cant I enter a different google account to a old phone after factory reset?

[Android Central Question]

My little sister wanted my old phone, so I factory reset it for her but now we can't access her google account. What should we do?!
It prompts a message about 24 hrs waiting for security

 

[B. Diddy]

Welcome to Android Central! Google's Factory Reset Protection requires the original owner of the phone to remove his/her Google account from the phone prior to the factory reset. Otherwise, if you don't, the phone will prompt the user to enter that account and password in order to proceed. This is intended to discourage thieves from stealing a phone and doing a simple factory reset to make it their own.

The phone is presumably asking for your Google account/password. Have you entered it, and it's still telling you to wait 24 hrs? Did you change your Google password during this time? Or did someone else own this phone before you?