If you don't have autogen at LGSK Skiathos and/or EDDN Nuremberg, the reason is a conflict with another add-on which has higher priority than our scenery.
The layering system of Prepar3D is not very clear, for example:
If Skiathos is below a scenery which covers a bigger area in your scenery library, Skiathos misses autogen.
If however Skiathos is above that bigger area, both Add-Ons have autogen. This shows that layering your sceneries can be a bit tricky. And unfortunately, there is no option in Prepar3D for layering your Add-Ons (added via add-on.xml) quickly. You will have to edit simulator files manually.
1. Do you have ORBX Central 4 installed?
ORBX Central 4 has the option to set the Insertion Point for their sceneries. Often, their sceneries suppress the Skiathos autogen because they are bigger in size. This also applies to EDDN Nuremberg in conjunction with FTX Germany South.
So the first step is to set the Insertion Point of ORBX below those sceneries which are missing autogen.
Here is a screenshot of the setting in ORBX Central 4:
In this example, selecting "Sharurah" will place the ORBX sceneries below our sceneries, which will bring back the autogen at EDDN Nuremberg in conjunction with FTX Germany South.
If you DON'T have ORBX Central 4 installed OR setting the Insertion Point did not help, we have to layer LGSK Skiathos manually:
1. Launch Prepar3D and open your Scenery Library,
scroll all the way to the bottom and take note of the highest number in the priority column:
1.1. Close the simulator
2. Open the folder "Documents/Prepar3D v5 Add-Ons/29Palms - LGSK - Skiathos" (for v4 open the corresponding folder)
3. Open the add-on.xml with a texteditor such as Notepad.
You will see the XML-content of the file. At the top there is a section called <Category>Scenery</Category>
and inside of that tag there is a <Layer>XXX</Layer> section. If the <Layer> section is not there, simply add that part to the file. The file should then look like the screenshot. Inside the <Layer> section, fill in the highest number you have found in step 1. and add 1 to it.
In this example, the resulting layer number is 147 which means Skiathos is now at the top of your scenery library.
If you don't have the <Category>Autogen</Category> section, simply add the following code snippet to the add-on.xml and adjust the <Path> content accordingly, depending on the installation location of your simulator.
The result should look similar to the screenshot below.
<Path>E:\Prepar3D v5\29Palms\29Palms - LGSK - Skiathos\autogen</Path>
4. Launch the simulator and verify that Skiathos is now at the top of your scenery library. Launch a flight and check if the autogen ist there.