It is not uncommon for leaders to forget the username or password they set for the group they have registered for an Event.
The good news is however, EvBoo provides ways to get a username reminder and allows for users to reset their own password. The video below walks through how to do both those things.
If that does not resolve the problem, we recommend you speak to your Event Admin Team or if you are part of the Event Admin Team, send an email to our support team.