replace the batteries on the ‘s’ gate
turn on the ‘s’ gate and check the lights are blinking
make sure Bluetooth is turned on
distance to the ‘s’ gate must be less than 200 feet (athletic) or 400ft (equestrian)
delete the app and reinstall it, answering yes to all the questions requesting permissions
try another iphone or ipad
Android phones: make sure Location is enabled (Settings->Location)