I cant open my elytras

**As you know you can use the rockets in the ground and tap twice spacebar to fly with the elytra but mine doesnt open and only make like boost jumps and fall over, i need to waste like 20 rockets to make my elytra open and it is very annoying, im on a realm, my friend says that he can fly without problems but i cannot, also i tried it on a world on creative and i can fly perfectly with one rocket, pls help :(I