What will happen when a user tries to join a full meeting room?

If you are the meeting host, you will get a message "Someone wants to join the meeting but the room is full". You can upgrade your U Meeting plan to allow more participants to join the meeting.  

If you are the user who is trying to join a full meeting, you will get a message "The meeting room is full". You can only wait for someone in the meeting room to leave the meeting or for the meeting host to upgrade his/her U Meeting plan.