openldap replication

I'm trying to configure replication between two hosts using the following as a guideline:

https://www.server-world.info/en/note?os=CentOS_7&p=openldap&f=5

Here are some notes I have based on the setup I've done:

##### REPLICATION ON Master #####

[root@ldap01 ~]# more mod_syncprov.ldif
dn: cn=module,cn=config
objectClass: olcModuleList
cn: module
olcModulePath: /usr/lib64/openldap
olcModuleLoad: syncprov.la

[root@ldap01 ~]# ldapadd -Y EXTERNAL -H ldapi:/// -f mod_syncprov.ldif
SASL/EXTERNAL authentication started
SASL username: gidNumber=0+uidNumber=0,cn=peercred,cn=external,cn=auth
SASL SSF: 0
adding new entry "cn=module,cn=config"

[root@ldap01 ~]# more syncprov.ldif
dn: olcOverlay=syncprov,olcDatabase={2}hdb,cn=config
objectClass: olcOverlayConfig
objectClass: olcSyncProvConfig
olcOverlay: syncprov
olcSpSessionLog: 100
[root@ldap01 ~]#

[root@ldap01 ~]# ldapadd -Y EXTERNAL -H ldapi:/// -f syncprov.ldif
SASL/EXTERNAL authentication started
SASL username: gidNumber=0+uidNumber=0,cn=peercred,cn=external,cn=auth
SASL SSF: 0
adding new entry "olcOverlay=syncprov,olcDatabase={2}hdb,cn=config"

[root@ldap01 ~]#

##### REPLICATION ON Slave #####

[root@ldap02 ~]# more syncrepl.ldif
dn: olcDatabase={2}hdb,cn=config
changetype: modify
add: olcSyncRepl
olcSyncRepl: rid=001
provider=ldap://172.19.33.42:389/
bindmethod=simple
binddn="cn=admin,dc=ZZZ,dc=ZZZ"
credentials=password
searchbase="dc=ZZZ,dc=ZZZ"
scope=sub
schemachecking=on
type=refreshAndPersist
retry="30 5 300 3"
interval=00:00:05:00

[root@ldap02 ~]# ldapadd -Y EXTERNAL -H ldapi:/// -f syncrepl.ldif
SASL/EXTERNAL authentication started
SASL username: gidNumber=0+uidNumber=0,cn=peercred,cn=external,cn=auth
SASL SSF: 0
modifying entry "olcDatabase={2}hdb,cn=config"

[root@ldap02 ~]#

# Testing LDAP
ldapsearch -x -b 'uid=testaccount,ou=People,dc=ZZZ,dc=ZZZ'

Both LDAP hosts work in the sense that I can authenticate to them. But replication is not working.

Please help.

TIA