GoToWebinar tech help

I'm having an issue with the iOS app on my iPad and iPhone. GoToWebinar refuses to use any of my blutooth speakers or headphones as an output. All of my other apps connect to them just fine, so I know there's no issue with the devices or headphones/speakers. Does anybody know why GoToWebinar is refusing to recognize them, or how I might fix it?
Devices in question - iPad (iOS 14.4), iPhone Xs (iOS 14.4.2), pairing with either BOSE soundlink, JVC car audio system, JBL headset, or Beats earbuds. No combination seems to work.

I've tried working with GoTo's own tech support but frankly they've been useless. This could prevent me from being able to participate live for a while, and I'd really miss that.