My FaceTime won't connect

See If you can't make a FaceTime call on your iPhone, iPad, or iPod touch https://support.apple.com/en-us/HT204168 or If FaceTime isn't working on your Mac https://support.apple.com/en-us/HT203585

Make sure you have data or wifi to transmit. Try to restart the phone or switch airplane mode off and on and try it. You also might try moving to an area where the data or wifi signal is better.