Choosing seats after entering credit card info but before finalization there is an issue:

I tried to book a trip several times on both mac/pc firefox, safari and chrome and had this issue. After I put in the emergency contact info (international reservation) I am told the reservation can not be processed and to try again. I kept trying and finding the same issue. The last time I decided not to pick my seats before purchase and everything went fine. Discussed this issue with the website help desk. Not sure if that will do anything good.