I can't get this to work at all, even for one of their "test" sessions.
On the main screen of the app, I typed the session number, and it brings up an alert saying I need to download the app. The button on the alert sends me back to the App Store, which confirms I've already downloaded it, and sends me back to the app.
I tried going to the support page and clicking the link there, and it just sends me to a blank white page in Safari.
I tried a different device (running a newer version of iOS), and it shows a webpage that says "Tap to join the session", and when I tap it, it says "Safari cannot open the page because the address is invalid".
I tried entering the meeting number from within the app, on the newer device, and it shows a spinner, darkens the screen, then half a second later resets the spinner and darkens the screen even more, and this repeats forever.
GoToTraining has some serious QA issues. I've tried to join their "test session" in 6 different ways (via the app, via the webpage, via the support link, each with 2 different devices), and they all fail -- and each in a unique way! Their support page is useless, too. If there's some secret trick to making this app work, I'm not smart enough to figure it out.
All video conferencing software is bad, but this is somehow the worst of all.