Fixed it. Just made some additions to the add-on.xml file. Some items were missing. See attached photos.
What's missing ? The add-on.xml created by our installer doesn't miss anything, and it should look like this, assuming an installation in the default folder:
<SimBase.Document Type="AddOnXml" version="4,0" id="add-on">
<AddOn.Name>FsDreamTeam KORDV2</AddOn.Name>
<AddOn.Description>FsDreamTeam Chicago O'Hare V2 International Airport scenery</AddOn.Description>
<AddOn.Component>
<Name>FsDreamTeam Chicago O'Hare V2</Name>
<Category>Scenery</Category>
<Path>C:\Program Files (x86)\Addon Manager\FsDreamTeam\KORDV2</Path>
</AddOn.Component>
<AddOn.Component>
<Category>Scripts</Category>
<Path>C:\Program Files (x86)\Addon Manager\FsDreamTeam\KORDV2\Scripts</Path>
</AddOn.Component>
<AddOn.Component>
<Category>Effects</Category>
<Path>C:\Program Files (x86)\Addon Manager\FsDreamTeam\KORDV2\Effects</Path>
</AddOn.Component>
</SimBase.Document>
There's no need for separate Scenery Textures components, when the scenery path is expressed this way:
<Path>C:\Program Files (x86)\Addon Manager\FsDreamTeam\KORDV2</Path>
That is, without ending with \Scenery, it means to add BOTH the Scenery and Texture folder underneath to the simulator. This form is supposed to be more efficient.