There seems to be an inconsistency while using the gui to add an authentication server (ldap) for access gateway. Things like ldapbinddn, ldapbinddnpw, ldapbase and others get completely lost or are saved incompletely.
Best would be to use the cli to add the authentication server...
cli (AD example):
add authentication ldapAction <NAME> -serverIP X.X.X.X -ldapBase "DC=domain,DC=com" -ldapBindDn "
user@domian.com" -ldapBindDnPassword GEHEIM -ldapLoginName samAccountName -groupAttrName memberOf -subAttributeName CN