Issue on one moderator and 2 users

Hi,
Please help me on this issue.

Have started the event with one moderator and 2 users: were the users cant see the moderator.yet moderator can see all of them.

After that logged in to the event with 2 users and one moderator. then we can see. after some time users were left from the event automatically so we have login again to the event.

Thank you for your time.