There could be several reasons. First, make sure you are dialing the correct access number and the correct password. If you enter an incorrect password three times, the system will lock you out. This is a security feature to prevent others from accessing your private voicemail. If you are locked out of your voicemail, when you attempt to login you will be told to contact the Help Desk (<a href="mailto:firstname.lastname@example.org">email@example.com</a> or x4476). If you are calling after hours, leave a message including your name and your extension. The system administrator will unlock your mailbox as soon as possible.