When I connect my Major 4 headphones to the phone using a 3.5mm cable (I have 3 different ones, the issue is reproduced on all three) the only thing I can hear is very loud white noise. Headphones themselves work fine when connected to other sources of sound, and my zf9 seems to work fine with other headphones.
I experienced the same issue on zf8 a long time ago.
while logged in, go to the admin's profile https://zentalk.asus.com/t5/user/viewprofilepage/user-id/293649
then there would be a "send a message" button
if it's not there, try to log in again
however, I'm not sure if it works since I didn't get any confirmation