Mujoco - Unity Plugin Crash - 2.2.1 on 2020.3
I downloaded the latest 2.2.1 version of Mujoco, both windows binaries and source code. I am running Windows 10, Unity 2020.3.36f1. Create a vanilla 3D project from unity hub I imported the package from source code (using package.json) as suggested. I copied the DLL in place. I imported arm26.xml in unity (after checking it out in simulate program) Saved the scene, hit play, crash!

If it's worth noting, I installed 2021.3.6f1, same issue. I made sure there are no floating mujoco dlls of earlier releases, deleted them all.
Had a false alarm for 2.2.0, It's working correctly now, (it probably copied the wrong dll?) I am reverting to 2.2.0 until we figure this out.
Great job on the plugin though, keep it up, you are making history!
I have met the same issue, also reverting to 2.2.0 solved the problem.
Unity -- Project. Folder Package (where you put the mujoco.dll in this folder). Select this mujoco.dll. And see the Unity Inspector. Click Editor (ticked). Click Apply. Works with (https://github.com/deepmind/mujoco/releases) mujoco 2.20. Make sure you copy the mujoco.dll from the unzipped folder (mujoco-2.2.0-windows-x86_64\bin) to your User folder (C:\Users\YourName\MuJoCo\bin)
Closing this for now, please re-open if the issue persists.