I had nearly the same problem, but started a meeting with 1 participant only. I copied the invitation to the meeting once I started the meeting and pasted it into an email. She used the link on the first try. She never showed up to me, as the host, that she was waiting to be admitted but she reported that she was in the waiting room.
I asked her to leave the wait room and sign in with the meeting ID and password, which she did. That worked, but then had the same problem again later. She used the meeting ID and password again and this time it did not work. Super frustrating. We decided it was taking too much time.