ldap filter not working

[MarvinKlar]

Hello everyone,

I currently try to configure Discourse to only allow users in a specific ldap group to log in.

My plugin configuration:
ldap enabled: true
ldap hostname: the hostname of my ldap server
ldap port: 389
ldap method: plain
ldap base: the base of my ldap server
ldap uid: userPrincipalName
ldap bind dn: Nothing
ldap password: Nothing
ldap filter: (&(userPrincipalName=%{username})(memberOf=cn=[the name of the required group],ou=....,[base]))

When using this configuration, nobody can log in to the forum. When I use the bind dn and password, everybody can log in.
I also tried this filter without success (copied from my ldap servers filter): (&(&(&(userPrincipalName=%{username})(memberOf=[dn of the group]))))

What do I have to configure, to only allow users in that specific group to log in?

I didn't found any errors or indicators in the log. Please help!

Thanks fou your help and attention!

[Victor-Morel]

Same error, I have a omniauth_error when applying a filter

[Victor-Morel]

My problem was solved using this comment