If Game Pigeon is not working on your iPhone, there are a few possible causes. First, make sure that you have the latest version of the app installed. If you don't, try updating it. Additionally, make sure that both you and the person you are trying to play with have a strong internet connection. If that still doesn't help, try restarting your phone and then your game app. If that still doesn't work, you may need to reach out to the app's support team for further assistance.