Please see the answer in the FAQ – #2.24: https://www.nextscripts.com/support-faq/#a24
All our scripts are installed on your server and your server makes posts to your networks directly. When you make a post your server logins to your account on your behalf and makes a post. The location that Facebook is asking you to confirm is a location of your server.
The further your sever from your home the more suspicious Facebook about that login. Please confirm that it was you. It might take several times and then Facebook will stop asking. Basically Facebook needs to mark your server IP as your “usual login” location. Once that happens, Facebook will stop with “suspicious activity” alerts.
Alternatively please try to use session instead of username password or vise versa.
Session Instructions: https://www.nextscripts.com/snap-nextscripts-api-for-facebook-configuration/#session