Unable to using LDAP using company AD without OU structure

Could you pls confirm if setting LDAP needed AD with OU structure?

ldapsearch which can query user’s object of our “CORPHQ” domain:
ldapsearch -D “CN=PMOSystem, CN=Users, DC=corphq, DC=hk, DC=pxxw, DC=com” -w XXXXX -p 389 -h corphq.hk.pxxw.com -b “CN=Users, DC=corphq, DC=hk, DC=pxxw, DC=com” -Z -s sub “(objectclass=*)”

but empty result set returned from gitlab ldap check:
sudo gitlab-rake gitlab:ldap:check
LDAP authentication… Success
Checking LDAP … FInished

Pls help, thanks.

As this is not allowed to create OU structure for Gitlab in our company.