This may help - perhaps confirm the ports between epo/ldap server are open/same
Unable to authenticate with the LDAP server. Verify the username and password are correct (ePolicy Orchestrator is unable to connect to an LDAP server) Technical Articles ID: KB66105 Last Modified: 3/31/2016
- If you use SSL, specify the correct port. Port 636 is commonly used for LDAP over SSL.
- If you do not use SSL, verify the port number. Not specifying a port will default to port 389, which is the normal port for LDAP without SSL.