Honestly not entirely sure which mod is the culprit here, but the Coupling from Create doesn't work on Immersive Engineering's Minecarts. Doubly unusual since it works just fine with the Minecarts and Pushcarts added by More Minecarts.

Additionally, the Coupler from More Minecarts and the Chain-Coupling feature of Quark both work on Vanilla, MM, and IE carts just fine.

I'll link this issue in both repositories since I'm really not sure where the cause is.
BluSunrize/ImmersiveEngineering#4663

Minecraft 1.16.5
Forge 36.0.42
Create 0.3e
Immersive Engineering 4.2.1-131

This issue has been marked as stale because it has been inactive for 3 weeks. It will be closed if it remains inactive for another 3 weeks.

This issue has been closed since it has been inactive for 3 weeks since it was marked as stale.