There are occasions when a horse is being stubborn and won't jump. The horse may be scared due to previous injury when jumping, he may not see the jump or he may not know what to do.
Examine why the stubborn horse won't jump. If her ears are back and she shies away from the jump at the last minute, she may be scared of it. If she swerves away from the jump with the intent to avoid it, she may not know what you want her to do or she may be taking advantage of you as a novice rider.
Step2
Work from the ground up to get a young, stubborn horse to jump. Start with a lunge line and a cavaletti. If the horse begins to cooperate with that, make a small, low fence at the far end of the cavaletti and have your horse jump over that. Continue doing this for several weeks.
Step3
Climb up in the saddle and work with your horse on the cavaletti. Stay relaxed as the horse can feel your tension. Allow him lots of rein to improve his confidence and get him to jump.
Step4
Consider the fact that the stubborn horse may want to take advantage of you. If you're new to riding or you lack confidence the horse can sense it and will do the minimum that he can get away with. Be assertive and relay to the horse that you are the one in charge and he must jump.
Step5
Paint the jump a different color if it is the same or similar in color to the ground. The colors may blend and the horse might not see the jump until it is too late.