Accounts are commonly created for events, and as such, the ability to log into the account may be locked until the morning of the even and will expire the night of the event. For example, an event that lasts from Monday to Friday will give accounts network access from 12:00AM Monday and will revoke access 11:59PM Friday.
If you need access after the event then please contact the event organizer, or register as a guest if access is needed immediately.