1. Click â€œTest postâ€, get the â€œ[message] => checkpoint_required [error_type] => checkpoint_logged_outâ€ error.
2. Open Instagram on your phone, login to the account you were trying to setup. it will say â€œSuspicious Activityâ€, and it will ask you to confirm it via app, sms or email. Confirm it.
3. Immediately Click the â€œTest postâ€ again, it will be working.
Important 1: DO NOT USE BROWSER to confirm. Instagram browser app is very limited. You must use your phone.
Important 2: DO NOT change your password. Password change invalidates all logins and makes all other login locations as suspicious.
Important 3: You may need to repeat those steps couple times.
PS: If you already tried to confirm it from your browser many times, you may need to wait several days until you will be able to confirm the login.