There are a few reasons ‌your hula hoop might keep falling down. First, check to ensure the hoop is the right size for your waist. If the hoop is too big, it's challenging to keep it spinning. Second, make sure you are using your arms to stabilize the hoop. Keep your arms parallel to the ground as you hula hoop. Finally, try slowing down the pace of your hoop. The hoop can lose momentum and fall if you move too fast.