Troubleshooting Online Presence and Instant Messaging Integration (Windows SharePoint Services 2.0)
Online presence information doesn't appear
Does your account have an e-mail address specified? The presence information appears only when the e-mail address for a person is specified. A user with a blank e-mail address that has only the DOMAIN and username specified will not appear as online.
Do you have a Windows SharePoint Services-compatible client installed? You must have a compatible client such as Microsoft Office 2003 to view presence information.
Is the virtual server for the site configured to display online presence information? By default, this feature is turned on. However, an administrator may have turned this feature off.