LDAP Server: Can't Add LDAP Server

Hi everybody,

I'm new to Drupal community, and I'm trying to add a LDAP Server in Drupal for the first time.

I fill (only) the following fields trying to add a LDAP server, but I cannot accomplish it:

[In CONNECTION SETTINGS]:
- Machine name for this server configuration (I'm filling a string like "test")
- Name (I'm filling a string like "test")
- Enabled (yes)
- LDAP Server Type ('Active Directory')
- LDAP server (I'm filling a string like 'ldap://domain.mycompany.com')
- LDAP Port (389)
[In BINDING METHOD]:
- I'm choosing "Service Account Bind"
- DN for non-anonymous search (something like USER@domain)
- Password for non-anonymous search (I'm filling its password...)
[In LDAP USER TO DRUPAL USER RELATIONSHIP]:
- AuthName attribute (I'm filling 'sAMAccountName')
- AccountName attribute (I'm filling 'sAMAccountName')
- Email attribute (I'm filling 'mail')
- Expression for user DN. Required when "Bind with Users Credentials" method selected. (I'm filling something like 'OU=P&D,DC=domain,DC=mycompany,DC=com')

Once I click on 'Add' trying to save the server I get no error message... however, no LDAP Server is added to the List.

I am doing something wrong?

Hope someone can help me.

Thank you!
Best regards