The connection status of each LDAP server is displayed in column [Status].
Green dot:
The connection to the LDAP server is established.
Orange dot:
The connection to the LDAP server is not checked or the connection is being checked.
After a reboot of the system, the dots are orange. Click [Test connection] to update the state of each LDAP server.
Red dot:
The connection to the LDAP server cannot be established. Check the settings of the LDAP server.
The following checks are done :
Connect + bind to the server using the 4 settings you have specified;
Read of RootDSE;
Probe for a user entry to enumerate user attributes;
Probe for a group entry to enumerate group attributes.