After doing a factory reset, it wants you to sign in as the original owner. This is a workaround. Go to settings and add user. Here's how:
When it asks for Google email:
Type a bunch of letters, press and hold to copy> choose assist> type or say settings> (in the settings menu) select add user> add YOUR Google email info.
When you choose assist, you will get a Google search bar. Type settings in that search bar and choose "enter" or "go". It will take you to the tablet's settings page. On that page, look for users, add user, manage users or something similar. (It varies by tablet brand)
It will take a few minutes to set up your new profile.
The original owner's profile is still there, but the tablet is completely usable. I haven't figured out how to remove it yet.
I hope this works for you too!!