Bluetooth Photive BTH3 headphones can't answer FaceTime calls

I'Ve used these headphones for a while and they work fine. On my iPhone 5s I can answer and end calls with one of the buttons. But as soon as I try my iPad mini it doesn't work. But use my iPad for FaceTime so I want this feature on my ipad but it doesn't work. It only works on my phone. Is there any way to fix this issue?