I've got a bunch of UA miles I'm looking to use, but I'm not a UA elite, so I'm trying to avoid $25 telephone booking fees, if possible. I also have never booked anything quite this complicated, so I'm not sure if I'm trying to do a routing that isn't allowed or if the online system just can't handle it.

Here's the overview of what I'm trying to do:
IAD-HKT (open jaw)
BKK-IAH (stopover)
IAH-IAD

When I search each of these routes individually as one-ways I am coming up with saver availability, however when I combine them into a multiple destination routing, saver seems to disappear on me. Any recommendations?

If it helps, these are the options I have for each route:

IAD-HKT
IAD-FRA-BKK-HKT (and other similar European routings)

BKK-IAH
BKK-NRT-IAH
BKK-FRA-IAH (I'm assuming I have to use this one?)

Then direct IAH-IAD.

Any thoughts as to why I can't get this to show up online? Will it work if I call?