The new webapp from Cisco removes one feature that was used in the old version: creating a URL that would pre-fill the call-id (the call-id, or meeting-id, is used to identify the virtual meeting room you want to join).
Such a link would look like this:
When you clicked this, you would be taken to join.vnor.com and the app would put you at the join screen with the call-id set automatically. Like this:
When the new webapp is activated, it will no longer pre-fill the call-id for you. Anyone clicking such a link will be sent to the start of the join process where you're asked if you want to "sign-in" or "join meeting".
This is how it will look if you click such a link after the new webapp has taken over:
For instructions on how to join as a guest, check this article: