Is my account enabled to use the Instant Join app?
When the Instant Join app is enabled for an organizer's account, then all attendees who join their sessions have the option of joining via the Web AppInstant Join app. When it is disabled, they must join using the desktop app or mobile apps.
If you are an organizer, you can check to see if the Instant Join app is enabled by logging in at https://global.gototraining.com and clicking Settings in the left navigation. On the Instant Join tab, you can see a check box that enabled and disables the Instant Join app for your trainings.
Note that if you are an attendee joining someone else's session, then it is up to the scheduling organizer of the session to enable the Instant Join app for their sessions you (even if you are also an organizer yourself).