Sembly joins your meetings as a guest, and it is common for conference platforms to have the lobby (waiting room) enabled for guests even if it is disabled for meeting attendees. With this configuration, Sembly agent will be placed in the lobby before the meeting starts and will need to be admitted by the meeting organizer or the designated user.
However, if you disable the lobby, the Sembly agent will be able to join the call without requiring permission to do so. Here you can read instructions on how to do it:
Unfortunately, it is not possible to disable the lobby feature in Google Meet as it is a default security feature to prevent unauthorized users from joining a meeting. Nevertheless, they offer an alternative - Quick access option.