Can you modify the file /usr/lib/one/ruby/opennebula/ldap_auth.rb around line 148 and add the line that starts with STDERR.puts?
def is_in_group?(user, group)
STDERR.puts "(#{@options[:group_field]}=#{user.first})"
result=@ldap.search(
:base => group,
:attributes => @options[:group_field],
:filter => "(#{@options[:group_field]}=#{user.first})")
After that try to authenticate and send again the log. You don’t need to restart OpenNebula.