I got it working fine with the Active directory:
Make sure the correct branch is selected in the settings, maybe thats
an issue.
My LDAP settings in Gerrit:
[ldap]
server = ldap://
10.0.0.2
username = DOMAIN\\admin
accountBase = OU=Desktops,OU=User AD
Policies,DC=xxx,DC=xx,DC=edu
groupBase = OU=Desktops,OU=User AD
Policies,DC=xxx,DC=xx,DC=edu