If you use the auto completion of scenProc to select the object, the tool will take care of the conversion between the FS2004 and FSX format of the GUID.
Did you add the new class in the correct region? Else they will also not show up.
I'm clearly on the correct path... I understand now the default.xml GUIDs are different than the one ScenProc shows format wise.
And took the time to reread the SDK on Autogen with tutorial however I am going about this creating model and converting them using
ModelX Converter not 3ds.
Using the SDK ContentScan.exe I receive this error which is most likely the real problem.
C:\Program Files\Lockheed Martin\Prepar3D v4 SDK 18.104.22.168097\World\Autogeneration>contentscan
AC2Scan Error: 1 : agn_TheWallP3D in default.xml contains a reference to a model (fb73f8e1-c57d-4aed-93ea-30f7998ba05f) that is not defined: K\TheWallP3D\agn_TheWallP3D
... for each region.
adding class region library code by AutoGenEditor.exe
- placed back in C:\Program Files\Lockheed Martin\Prepar3D v4\Autogen
} created using ModelXConverter
} rendered from ScenProc