The app primarily uses the movement of the physical phone and not the speed to detect the gait (How does Equilab measure the gait?) So to be able to get an accurate record of your ride you need to carry the phone with you and you need to be on the horse. It is moreover important that you keep your phone in a tight fitting pocket or in a sportsband on your arm to get good accuracy.
For Carriage Rider
Since Equilab uses the movement of the phone to detect the gaits you as a carriage rider need to place the phone directly on the horse for you to get accurate detection. We highly recommend you to be very careful if you are doing this since something may happen during the ride that can destroy your phone. If you don't want to put the phone on the horse you can as well add trainings manually in the app after each training session.
Still doesn't work
If you are doing all of the above and it doesn't work for you then checkout our guide on problems with gait detection: