BA award search keeps saying no flights, am I missing something?

Trying to book a business class award from ARN to AUS using Avios and BA’s site keeps telling me there’s no availability at all.

I know there’s no nonstop on that route, so I’m obviously fine with connections. What’s confusing me is that when I search the same dates on AA’s site, I see plenty of connecting options in business.

This is my first time trying to redeem Avios and I’m wondering if BA’s search just doesn’t show partner connections very well, or if I’m doing something wrong on my end. Do I need to search segment by segment, or is calling BA the only real option here?

Any tips from people who’ve booked similar long haul awards with BA would be appreciated.