you are probably running android 5.1 on it and it has entered factory reset protection (FRP). There is a way to get back into it but it is a lengthy process. first off there are two ways to do a factory reset. 1 the key combo reset and 2 the backup and reset setting menu. the key combo one does not erase everything it actully still saves the users email address and password and wont let you get back on it unless you input the correct username and password. you need the second one with the security menu. to get here you need to start the log in process but do not type in your email hold down the , button on your keyboard and you should see a setting icon appear go to that you will see a window pop open go to the one below languages. now you need to get to a help section it doesn't matter which one as long as there is a lot of text that you can hold on and get to the share menu don't click on share click on the search icon (the magnifying glass) and type in settings you should see settings appear click on that. once you are in the setting go to backup and reset and click on factory data reset. wait for it to reset and you should be able to set it up like its a new phone. make sure your phone is fully charged before this process. this process is a little different on all phones. I am not responsible for any damages that may occur during this process.