If you look at
http://fgfs.goneabitbursar.com/pkg, you will see that packages exist for versions 3.1.0, 3-2.0, 3.3.0, 3.6.0 and 3.7.0. They do not exist for versions 3.4.0 and 3.5.0.
I assumed when the problem first manifested itself here with version 3.4.0 that it ws because the package had not been uploaded.
The error messages persist when I checked today, and so I did some ivestigation and found the above results. It is obvious that there is another problem.
I have deleted everything on C:\Users \Alan\Appdata\Roaming\flightgear.org. The directory C:\Users \Alan\Appdata\Roaming\flightgear.org\Aircraft, which held the old default directory, is not regenerated when flightgear is run.
This is in C:\Users \Alan\Appdata\Roaming\flightgear.org\fgfs.log:-
general:5:..\..\simgear\package\Catalog.cxx:93:catalog download failure:http://fgfs.goneabitbursar.com/pkg/3.7.0/default-catalog.xml
io:4:..\..\..\src\Network\HTTPClient.cxx:79:refresh of Catalog
http://fgfs.goneabitbursar.com/pkg/3.7. ... atalog.xml failed:4
io:3:..\..\..\src\Network\HTTPClient.cxx:57:all Catalogs refreshed
failed:4 indicates "FAIL_DOWNLOAD" according to the simgear source code.
I will cross post this to the devel list.
Alan