I will leave some tips for anyone who are trying to make this plugin work on AD (Active Directory):
1) At "Connection Settings" make sure you are setting the search user correctly (add the domain spec like: MY-DOMAIN\USER). And then check the option "Test Connection" before saving. You should see a "Connection Successful" message.
2) At "Attribute Mapping" pay attention on every AD attribute. The "Distinguished Name (DN)" attribute on AD is "distinguishedName" and not "dn". The "Phone" is "telephoneNumber". Clear the Home Directory and Mac Address if your not sure about them.
And the last one...
Download this application to test your connection settings and attribute lookup:
I hope this may be useful for someone.