Asobo Blender Exporter - fatal error. Can't export objects

I have tested the exporter in July and it appeared to work, it did create a
proper file set for an object. However now, after a huge amount of time spent
in modeling a terminal in my project, when I tried to export, it throws an
error. What’s even worse, the file I tested on, back in July, also returns an
error. I installed Blender 3.1.2 and tried there - same error. All materials
are converted. Please help, I can’t work on the project if I can’t export the

location: :-1
Error: Python: Traceback (most recent call last):
  File "C:\Users\Roman\AppData\Roaming\Blender Foundation\Blender\3.1\scripts\addons\io_scene_gltf2_msfs\io\", line 171, in execute
  File "C:\Users\Roman\AppData\Roaming\Blender Foundation\Blender\3.1\scripts\addons\io_scene_gltf2_msfs\io\", line 45, in export
  File "D:\Program Files\Blender 3.1\3.1\scripts\modules\bpy\", line 132, in __call__
    ret = _op_call(self.idname_py(), None, kw)
RuntimeError: Error: Python: Traceback (most recent call last):
  File "D:\Program Files\Blender 3.1\3.1\scripts\addons\io_scene_gltf2\", line 651, in execute
    return, export_settings)
  File "D:\Program Files\Blender 3.1\3.1\scripts\addons\io_scene_gltf2\blender\exp\", line 46, in save
    json, buffer = __export(export_settings)
  File "D:\Program Files\Blender 3.1\3.1\scripts\addons\io_scene_gltf2\blender\exp\", line 71, in __export
    json = __fix_json(exporter.glTF.to_dict())
  File "D:\Program Files\Blender 3.1\3.1\scripts\addons\io_scene_gltf2\io\com\", line 1203, in to_dict
    result["materials"] = from_union([lambda x: from_list(lambda x: to_class(Material, x), x), from_none],
  File "D:\Program Files\Blender 3.1\3.1\scripts\addons\io_scene_gltf2\io\com\", line 56, in from_union
    assert False

location: D:\Program Files\Blender 3.1\3.1\scripts\modules\bpy\

location: :-1

Edit: This has something to do with materials. If I create a test cube with a
MSFS Srandard material it works OK and exports without errors - although all
images are named image.png, image-1.png and so on, instead of material name or
something meaningful. That also means multiple images for same materials on
different objects? But as soon as I change material from “Standard” to
“Parallax” (which I use extensively in my sceneries) - I get the same error!
What’s worse, if I check the “day/night cycle” checkbox even on “Standard”
material - I get the same error immediately! And checking “Collision Material”
results in the same error! So either “Parallax” or “Day/Nifht cycle” or
“Collision Material” do not work, and result in the fatal error. This is a
major disaster! I have spent a lot of time on creating an Asset Library and
converting/migrating all my materials (about a hundred of them) to the new
format. Now it turns out nothing can’t be exported, and basically this Asobo
Blender Exporter is unusable, because it can’t export parallax, day/night
cycle and collision, which I always use. Please tell me there’s something with
my setup that’s wrong and can be fixed, and it’s not a dead end…

I had exactly the same problem with same error message a while ago. How i
fixed it:

  1. Backup your project.
  2. Use Blender version 3.1!
  3. Reset Blender preferences to default with project open, then activate the MSFS exporter and only then save the project again. Make sure you have no other MSFS related importers or exporters activated in your plugin settings!

Also make sure to never save your project with several MSFS importers and
exporters enabled. Stick to one as it might break materials otherwise.

I think I solved this issue, though it took most of the day eliminating
different factors. In case it’s useful to others, here’s what helped: 1.
Installing Blender 3.1.0 - that exact version, newer versions may be
problematic. 2. Completely erasing blender user folder, where all settings
and addons are stored, and not importing previous Blender settings. So a clean
slate installation. 3. Fresh install of the exporter, 4. Adding and enabling
the addons that I need, one by one. So far it’s working, though I haven’t
tested in MSFS yet. But my test files are exporting without errors and are
creating plausible files. I have no idea what was corrupted in Blender
settings or anywhere else in the Blender user folder that has resulted in
those errors. But for now the issue is gone…

I posted my solution before I read yours, but it’s almost identical! Thanks
for the input.