The problem simply can't happen if you just install PHNL.
It can happen only if you uninstall it, then reinstall another scenery. In this case, and this case only, installing the Stand-alone Addon Manager is needed, so you'll get all the updates that came with PHNL, in case you don't want to keep PHNL installed.
As I've said in the other post, you should be using the latest version of the Stand-Alone Addon Manager: it's best if you CLEAR YOUR BROWSER CACHE before downloading it, because you might think to have the current version, but you haven't.
Or, just reinstall PHNL, because IT DOES have the correct files, exactly the same that come with the Addon Manager.
In both cases, you should do this with your other FSDT airports installed, otherwise the PHNL (or Addon Manager) installers can't update them.