I am trying to use Avios on AA flight from Houston to Maui via Phoenix. IAH-->PHX-->OGG-->PHX-->IAH

I am able to find award flights on AA's website, but not on BA. When I call BA they tell me there is no availability, not only for the days I'm looking for, but also for the month before and after.

What gives? Why is it so difficult to book a flight to Hawaii on AA using Avios?!

All tips/advice appreciate, thank you!