Ok,
so let's try to fix this step.
1. Can you temporarily colorize your objects, so we can identify the __airport__runway and the __airport__outside areas?
2. Make sure, your complete mesh is at elevation 0.
3. All __airport__runway objects have to have a texture file from the runway texture library. This is mandatory.
4. The __airport__outside must not have a texture.
4. In the TSC we have to set the object type to ground and the autoheight_override to -1
Code
<[tmsimulator_scenery_object][element][0]
<[string8][type][ground]>
<[string8][geometry][kcof_rwy]>
<[vector3_float64][position][-80.607804 28.239382 0]>
<[float64][orientation][0]>
<[int32][autoheight_override][-1]>
>
You may attach your TSC here. If you agree, even the .AC file. I will check it.
You're close to succeed! Le's do the last steps!