This function is not needed for core functionality of DbDefence however Client DLL rely on that feature to define if DbDefence is installed on that server and if there are any encrypted databases. If this function do not list any databases Client DLL do not display its dialog.

Note: On SQL Server Express databases has default option called AUTO_CLOSE ON. This feature is always ON when you attach or create database. If it is ON then SQL Server unloads unused database from memory. This behavior may lead to confusion. dbd_listdb will not display unloaded database and Client DLL will not display login dialog as expected.

To solve the problem set AUTO_CLOSE OFF for encrypted database as:

ALTER DATABASE DbName SET AUTO_CLOSE OFF

You need to do it every time where database attached to server. You can see current AUTO_CLOSE state for databases with the command: select name,is_auto_close from sys.databases

By default this option is OFF on SQL Server editions other than Express.