Problems Simulating Collision of URDF Bodies

Hi there,
I am trying to simulate scenes with imported URDF meshes in Isaac Gym. However, there seems to be no collision/contact simulation happening and objects keep passing through each other. I tried modifying example by adding a second mug in the mug environment falling on top of the other and observed the same problem. Any help will be appreciated.
BTW all the URDF files I have used do have collision models.

You mean collision between links of the same actor or between different actors in same environment or actors in different environment?

I am testing single-body un-articulated assets/actors like urdf/ycb/025_mug/025_mug.urdf; e.g. two instances of the mug in the same environment pass through each other when they should collide.

Actors who belong to the same collision groups can collide, otherwise they will pass each other. when creating the actors you should put them in the same collision group:
gym.create_actor(env, asset, pose, “actor”, i, j)
In this function “i” is the number of the collision group, it should be the same for actors which you want to have collision, “j” should be zero if you want links of an actor to have collision, otherwise it should be one!

Thanks @Abi64!
I set filter to 0 and it worked.