I was getting this same error going to the omanair . com website as well. If you google Oman Air flight booking this link should show Oman Air and when you click on this one then select Manage My Trips you can select seats in there. I have selected our seats in this site and the seat selection shows in Qantas app so it has fed through. It shouldn't be this hard!!!I had to call QF to get my WY booking reference. I can pull up the booking and add my phone and email but it won't give me an option to select a seat. There is an Add Seat link. When i click on it it says this.
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