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

Question

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.

Answer 1

Comparing your configuration to mine, I have a user_filter value
###! **remember to close this block with 'EOS' below**
gitlab_rails['ldap_servers'] = YAML.load <<-'EOS'
main: # 'main' is the GitLab 'provider ID' of this LDAP server
label: 'LDAP'
host: 'ADHostname.example.com'
port: 636
uid: 'sAMAccountName'
method: 'ssl' # "tls" or "ssl" or "plain"
bind_dn: 'cn=UserID,ou=SystemAccounts,dc=example,dc=com'
password: 'AccountPasswordGoesHere'
active_directory: true
allow_username_or_email_login: false
block_auto_created_users: false
base: 'ou=ResourceUsers,dc=example,dc=com'
user_filter: '(&(sAMAccountName=*))' # Can add attribute value to restrict authorized users to GitLab access, we leave open to all valid user accounts in the OU. Should be able to authorize based on group membership using linked attribute value like (&(memberOf=cn=group,ou=groupOU,dc=example,dc=com))
attributes:
username: ['uid', 'userid', 'sAMAccountName']
email: ['mail', 'email', 'userPrincipalName']
name: 'cn'
first_name: 'givenName'
last_name: 'sn'
EOS