To start troubleshooting from here you’ll need
ldapsearch queries to generate log entries to examine, and also view the returned information.
Figuring out the correct query might take some work, but starting with checking the
cn would be good.
To check if the user (here
user_of_interest as an example) is what you expect try something like
ldapsearch cn=user_of_interest where this is of the form
ldapsearch <filters> and add more filters as needed.
Check to make sure what is returned matches what you have set for things like the basedn and attributes in Apache are correct.
Make sure the user_of_interest has only one entry, that’s an issue that’s been seen before where there exists more than one entry and sometimes does not return the same user as expected. Hopefully this allows you to at least start generating queries to debug further.