Gitlab Authentication returns invalid username or password (LDAP pane missing)

I have users in active directory LDAP (each have a username and email set).
I configured LDAP authentication in gitlab.rb and ran “gitlab-ctl reconfigure”.
I user Gitlab Community Edition.
The following command returns the users so configuration seems ok “sudo gitlab-rake gitlab:ldap:check”.
Returns :

LDAP: … Server: ldapmain
LDAP authentication… Success
LDAP users with access to your GitLab server (only showing the first 100 results)

DN: cn=Mike Gordon,cn=users,dc=ad,dc=mydomain,dc=com sAMAccountName: mike.gordon

… here other users

I’m trying to login with LDAP username mike.gordon and corresponding password on “Sign in” gitlab pane but i get “invalid username or password”.
Some screenshots show that there is an LDAP pane but it’s not displayed even with :
gitlab_rails[‘prevent_ldap_sign_in’] = false

this is my configuration :

main: # 'main' is the GitLab 'provider ID' of this LDAP server
label: 'LDAP'
host: 'myAdUrl'
port: 3268
uid: 'sAMAccountName'
bind_dn: 'CN=serveur-ovh,CN=Users,dc=ad,dc=mydomain,dc=com'
password: 'adpassword'
encryption: 'plain' # "start_tls" or "simple_tls" or "plain"
active_directory: true
allow_username_or_email_login: false
base: 'dc=ad,dc=mydomain,dc=com'
user_filter: ''
#lowercase_usernames: false
#block_auto_created_users: false
#verify_certificates: true
#smartcard_auth: false
### EE only

Thank you very much in advance for you help.