Hello,
I recently experience a similar issue when I export my mission.
1. I imported a working mission from the 2d editor.
2. Made lots of modifications to the map meaning I added a ton of items using the 3D editor.
3. When I finished I select export and a mission file was created.
4. I go to my MP missions folder I can see the file its 3.4MB in size.
5. When I go into the game using the Dev mode I can create a multiplayer server and load my mission without any problems.
6. The issue I have is when I take my new mission to a system that does not have Dev loaded, the mission will no appear on the list of missions available.
7. I also tried to load the MP mission on the system that I used to modify the original mission, I turned off the Dev portion of the game and then tried to create a multiplayer server. No luck the file did not appear on my missions list.
I uploaded my mission on Steam Workshop you can find it under "Eden Export Test File" by Silent USC
So Far I've tried 2 missions but no luck.
Please Help