HTC Vive head calibration problem

I am currently doing this project with VR on unreal using HTC with a class. I have all my models ready and scaled correctly. However, once I play it in VR and as I pick up the headgear in VR it does not calibrate the height. The weird thing is, the controllers/hands calibrated the height of the person holding it which confuses me and my groupmates. Is it a collision problem? NavMesh issue? any help would be so much appreciated at this point.

PS. All the other groups are able to have the headgear calibrate their height.