Market sell orders "no longer supported" on Gemini

Hello, I am currently watching the “Creating Exchange Module” lesson, and I noticed something different between what I’ve got and what Ivan got when we both ran the function to manually sell BTC at market price.
Basically, I can’t seem to get my order filled at the lowest market price when selling for the price of virtually 1 USD.
This is what I get instead, from my Gemini sandbox:
I was wondering if something changed in the Gemini sandbox, because from what I’m noticing, it’s filling other people’s lowest limit buy orders. I might be wrong, though.
I made sure the code is the same as the one Ivan is typing during the lecture.
Manual market buy orders work just fine, on the other hand.
Thank you for your time.