The Invalid DN syntax (34) means the LDAP server did not receive a full DN or that you did not specify a correct prefix, such as CN instead of UID, which results in the LDAP server not receiving a correct DN.
The CA-LDAP Server determines the user id to use by looking for cn= as the very first RDN in the DN. The Invalid DN syntax (34) message can occur if just the userid is entered in the "User DN" rather than cn=userid.
To address the problem be sure to specify cn=userid in the 'User DN' text box in JXPLORER screen.
Note: in place of "userid" substitute the desired userid.
Details on the the "USER DN" specification for the JXplorer browser can be found at the JXplorer website.
Details on CA-LDAP can be found in the CA LDAP Server for z/OS Administrator Guide