I just went through a weird situation with United phone agent.

Today, ANA start accepting reservations for their new flight NH846 (SIN->NRT) and NH174 (NRT->IAH)

I try to book these two flights, along with some others, as the following:

ORD->ICN->SYD |7 days stop-over| SYD->BKK | 1 month | BKK->SIN->NRT->IAH->ORD

I am pretty sure my routing is valid (if not, please kindly enlighten me) and I already verify that all segment have an available seat. But, of course, United website gave me an error.

I called United reservation center, and got a lovely lady to assist me. Everything was fine until I mentioned SIN->NRT segment (NH846) and NRT->IAH (NH174) and she said she could not see the flight from both award and revenue inventory.

I already double-checked that both flight shows up on United.com and one can book it online (i.e., it is not a "phantom" award availability).

Any suggestions?

Edit:

I can book ORD->ICN->BKK and BKK->SIN->NRT->IAH->ORD online separately but combining them (in every combination I tried) results in an error.