In most countries, you would have to request a refund from Flighttix, the ticket seller.
In some countries, customer is protected by joint and several liability. In this case, if Flighttix is uncooperative, you could legally request a refund from Etihad.
You cannot, however, request a refund from both parties at the same time.
Etihad could possibly help you rebook your ticket on a new flight, but if you want a refund, you need to first contact the ticket seller.
Credit:stackoverflow.com‘