Specifying a bindDN that does not contain an ou= term will return Bind Error: Group not found, even though the same code conditionally checks for bind strings that do not contain that second term.

groupName is initiated with an empty value, and if you do not specify the ou= term, groupName does not get set in the previously-mentioned conditional block.

Because groupName does not get set, the backend will be unable to find the a matching groupname from the config file's groups. This search makes sense if you specify the ou= term but if you only provide the cn= you should still be able to bind.