@AshC I could still download the app from the link you provided. However, when I entered the meeting ID, it still popped up in a web browser. And I also didn't install any security app neither.
Do you know if you ever used a GoToMeeting 'Free' license on this account? If so, we may need to clear that out from the billing section of your online account.
What is the maximum number of Attendees you see in your Attendee pane while in session?
There are no trial restrictions that I'm aware of. I was asking in case you had an account with us some time ago.
Regarding this web app restriction, are you able to reset either FireFox or Chrome back to their default settings, then clearing the cache + cookies before a reboot and retest of the GoTo launch?
I'm not sure which security setting in particular, but I'm guessing the message received by GoTo is that you're not able to download or launch the Opener.