Hi,
In global airports, the file only seems to contain updates. (I am not 100% sure though). I have no HERICOURT NDB there neither.
I tested it myself and it worked. Make sure you can see the NDB in the map view, pay attention to the type of map, not all show NDBs. Try if you can identify it, from the sound panel (on top of the GPS, click on ADF1). You should receive the Morse code of HR which is [.... ._.].
Please note that if you want to update a whole cycle with Navigraph for example, the files should be placed in X-Plane 11\Custom Data. I have done it (so I do not use exactly the same earth_nav.dat file), but that wouldn't explain why it works for me and not for you.
Well, not sure what to do next..
Reset all failures, delete prefs files, read the file X-Plane 11\Custom Data\readme.txt...check the following page :
http://www.x-plane.com/kb/
All the best with that and let us know what you come up with.
Guillaume