Still seeing fees on BUSD trades... am I doing something wrong?

As I understand it, I should have a 0% maker fee when I'm trading pairs where the base currency is BUSD (taking advantage of the binance promotion that was extended through the end of 2021). But I'm still seeing fees charged when I fill limit orders for ETH/BUSD, BTC/BUSD, and MATIC/BUSD. Doesn't matter whether I set the limits myself on binance.us or run them via the bitsgap or 3commas API (I was worried the API was doing a type of limit order that didn't count as a maker trade... but even on limit orders set on binance.us I'm still seeing a fee). I tried disabling the 'pay fees with BNB' feature, but that doesn't impact it. Is there something I'm supposed to do to enable the promotion?

Thanks so much for your help - sorry if this is a n00b question.