You will need to edit or create a new Meeting policy and assign it to the account that has created the meeting invite.
The new Policy will need the below enabled:
"Let anonymous people start a meeting" this will allow the meeting to be started as soon as anyone joins.
The original meeting might need to be resent after this policy has been applied.
Or you can change the meeting options in the meeting itself by opening the meeting series (with the account that created the meeting) client on "meeting options" then changing the "Who can bypass the lobby?" option.
Hope that helps,
Regards,
T