The University has a number of licenses allowing people to access Colleague.  Occasionally, however, all the licenses are in use at the same time.  When that happens, other users will not be able to access the system, and an error message will appear.  See below.

There is not much that you can do except ask people in your area if they could close Colleague if they are logged into the system and are not using the application.  You should just keep on trying to log in until you can get in.