Not sure mine does either but I'll never use it. Collision avoidance was never one of the reasons I chose the H anyway.
Do read through the use instructions for CA and note that it only functions above a certain height and in a specific flight mode. Perhaps one of those qualifiers has not been met?
Landing gear up and down. Sometimes the CA works. Now the camera is always tilting. I think I go a lemon. Amazon is sending me a new one. I hope its just a fluke.