1.Why is the volume control of F9 not working on iPhone?
A： First of all, ever since iPhone 7, there are iPhones with 3.5mm headphone jack and without 3.5mm headphone jack. We could see from the trend that iPhone will directly use lightning earphones or Bluetooth earphones. And those earphones will certainly come with in-line remote control. And we will need the MFi certificate and dedicated chips from Apple to support the whole functions for the existing iPhones. Otherwise, we could only support Play/Pause for iPhones.
So far, only the F5 in-line remote control could be perfectly compatible with Android/Apple devices. And it has been authorized the MFi certificate. Our other earphones which have the remote control could only support Play/Pause with iPhone.
Besides, the previous iPhone before iPhone7 on the market are getting less and less. So our future 3.5mm in-line remote control earphones will not support the remote control on previous gen iPhones. Please kindly understand that.