Do you have no choice but to go through Asus? Wouldn't it be easier to contact the seller directly?
I'm asking because when my RT-AC86U broke down, I started off with Asus Poland - and it wasn't a pleasant encounter. When they finally picked up the phone (after more than two hours of calling), they were very non-committal, not to mention clueless. and just told me to send it over, of course at my expense. And they refused to answer my question as to whether the unit would be repaired or replaced, or if I could perhaps apply for a refund ...
So I contacted the shop instead, outlined my problem and asked for a refund - everything was sorted in three days.