It appears that adding more than one surcharge for Adults, Children, Guests, etc is causing issues in the AirBnb API integration. Originally, I set a surcharge for "Adults" over 4, and it seemed to work fine. But I started getting people with lots of children and wanted to include an additional surcharge, but only have it kick in after 6 total guests. So I made another surcharge that kicked in for "Guests" over 6. The idea being that 5 adults would trigger the "Adults over 4" surcharge, but 4 adults and 2 children wouldn't incur an extra fee. However, if someone had 4 adults and 3 children, then the overall 6 "Guest" surcharge would kick in.
However, when I added the second surcharge for guests, AirBnb stopped enforcing my Adults over 4 surcharge, and instead, only enforced the Guests over 6 surcharge. I set the Position on the two surcharges so the Adults over 4 charge would come first, but that didn't have any effect.
I guess I can't use both surcharges if I want it to work with AirBnb?
Yep, Airbnb only supports a single guest fee, and it applies to all guests -- there is no way to do criteria like you can for direct bookings.
You can read more about what's allowed on Airbnb rate settings in these articles: