Replication failing between RHDS Servers (Unable to get issuer certificate)

Issue

[07/Jan/2023:10:43:56.429182262 +0100] - ERR - slapi_ldap_bind - Could not send bind request for id [cn=replication manager,cn=config] authentication mechanism [SIMPLE]: error -1 (Can't contact LDAP server), system error -5987 (Invalid function argument.), network error 0 (Unknown error, host "server2.example.com:636")
[07/Jan/2023:10:43:56.430193864 +0100] - DEBUG - NSMMReplicationPlugin - bind_and_check_pwp - agmt="cn=server1-server2-replication" (server2:636) - Replication bind with SIMPLE auth failed: LDAP error -1 (Can't contact LDAP server) (error:1416F086:SSL routines:tls_process_server_certificate:certificate verify failed (unable to get issuer certificate))