I realize this discussion thread is a few years old, but on a 2019 16" Macbook Pro this is still an issue, so for those that are still suffering with this GoToWebinar problem, here's a simple workaround:
Go to System Preferences -> Accessibility -> Audio and select "Play stereo audio as mono".
It takes the sound that GTW is sending to just the right speaker and sends it out both (you might want to up your volume, it seemed to get quieter when I did this).
Once your meeting ends you'll probably want to undo that change to get full dynamic sound again.
Found this tip here:
Thanks for posting this tip Macxpert. I have been experiencing this same thing on my MacBook Pro and thought it was just my old ears failing.
I notice this only using GoToWebinar, so it must be something they are doing differently than every other program I use on that computer.
It blows my mind that it's years later and GoTo/Logmein hasn't bothered to fix this super obnoxious problem. At least add a checkbox in preferences! Thanks for the accessibility workaround suggestion.
Checking in to see if there is an update on this issue. This happens on all of my Macintosh computers. When running a GoToWebinar, only the right speaker works. With all other online meeting/webinar tools, sound comes out of both speakers.