[AC Question]

My galaxy s6 keeps saying it and wont go on anything...

[B. Diddy]

Welcome to Android Central! That happens if the phone is factory reset without first removing the Google account from the phone. When you finish the reset and try to set up the phone again, you have to enter the Google account information of the account that was on the phone before the reset. It's an antitheft measure. Do you not remember your Google account info, or did you buy the phone used from someone else?