"Too many concurrent users" indicates that the database is already being used by the maximum allowable number of users. Try to access the database at a different time.

It is recommended that users of this database do the following to limit concurrency turnaways and to allow for other users to gain access to the database: 1) Ensure all browsers are set to enable cookies or the system may log each individual piece of content on a page as a new request and register it as a separate session; 2) Log out completely after finishing a session. If the log out button is not selected upon exiting the database, it may take up to 20 minutes for the session to expire; 3) Use only one open browser per session. Multiple browser windows may be logged as separate sessions.