When updating the Directory Connector Domino credentials there is an error of "Could not open connection to server" when clicking Next on the Connector wizard.
This can be caused by the LDAP task not running on the Domino server.
On the Lotus Domino server that is specified in the Directory Connector ensure LDAP is listed in the ServerTasks of the notes.ini file. On the Domino console perform a Load LDAP to enable the task.
Note: Use netstat -ano to check for listening port 389 and test the connection to Domino via Telnet DominoServer 389.