They might have some issues viewing your meshes if you have created and saved them (the meshes) using the Default object groups. Often, if you add meshes that had been saved to a default object group, this will prevent others from seeing those objects, even if you can see them yourself. To fix this, try taking those meshes and instead of saving them to a default (a pre-made group that already existed in the game) object group, save them into a custom object group by creating a new object group. Once you've done that, re-export the map, and send the updated link to your friends. c:
Let me know if this helps!