I had the same issue last week with a award flight YVR to JFK. The first time it took around 12 hours to ticket in Business (kept getting the message saying it wasn't ticketed). But then I canceled the ticket and rebooked First - not sure if it was the time of day I did it but CX actually cancelled it, when I called BA they said there was a note saying CX had cancelled because BA didn't ticket in time - she was also surprised it didnt go through straight away, anyway the agent managed to rebook and sort it out while I was on the phone so suggest you call BA to check.