Vortex Sound Research

I’m trying to connect a theremini to a td-3 like I saw in Sweetwater’s td-3-mo demo video. Granted I don’t have the mo, but it seems like it should work the same. I’m using a Hosa 3.5mm TRS to 1/4” stereo cable to connect them, but I’m not getting any interactivity. I’m pretty new to electronic instruments, so any help or advice is greatly appreciated.