I bought the Realsimgear software. I use the GNS 430 in XP 12. I finally got it working. That was not easy.

Now I see that airports are missing in the database. EHTW is a former military airport.

Still active. However, I can't find it in the GNS 430. Not in the icao/IATA designation.

Did I miss an update here? If so, how can I get that update?

https://help.realsimgear.com/en/articles/3927413-how-to-use-navigraph-with-realsimgear-products

https://forum.navigraph.com/t/possible-to-update-the-nav-data-in-real-sim-gear-gns-430-530-and-or-gtn-650/5791

Thanks for the tip, however.
Tried this several times. Doesn't seem to work.

Then you need to contact Realsimgear's support.