SIGN-UP-BANS

The device is flagged. In your case since you are using emulators, we have tested this with 500+ accounts and 400/500 got flagged on emualtors. You are going to have to use real devices. Even with real devices, you can get flagged aswell in case you add new accounts all at once. You have to add accounts to the device very slowly so that you dont trigger a "Confirm You Are Human".