Hi Steve,
the syntax as such is correct, if I test this using objectclass=group, I get a correct result. I don't have the objectclass you mentioned on my AD, so I cannot test with that. Can you please verify if you added the Base DN as a start point of the ldap search, and not a different container? If there is no object found with that class in the PATH you defined, a 0 result for example would be correct. Also, when you run the test search on the profile you created, do you get an error?
Regards,
Martin