I wasn't there to see where you went wrong, but I know from my own experience that anytime I hit a reverse triangle that failed, it has been because I forgot about their arm and they had it framed. It also doesn't help that you are in a position where you can't see the choke to help you troubleshoot.
As others have mentioned, you need to drag their arm across just like a traditional triangle. If you can't get the choke, don't just give up and let go. Work for the sweep so you can get some benefit out of the position and, who knows, you might have better luck with it once you are on top.
As others have mentioned, you need to drag their arm across just like a traditional triangle. If you can't get the choke, don't just give up and let go. Work for the sweep so you can get some benefit out of the position and, who knows, you might have better luck with it once you are on top.