I posted this first in WebGL forum, but may be more appropriate here. This is the WebGL post https://forum.unity3d.com/threads/first-time-webgl-game-input-collider-dont-work.454356/ I have a couple objects, made in blender, and collisions are not working right in WebGL. At a loss to figure out what is going on. Details are in the linked post. I will update here if I find out anything.
I'm having similar issues. Oddly, the rotation of the mesh (made in blender) seems to be relevant to the issue happening for me. Details here: http://answers.unity3d.com/questions/1406530/in-webgl-build-rigidbody-only-collides-with-mesh-c.html
I have the same problem. Details here: https://forum.unity.com/threads/problem-with-mesh-collider-in-webgl-build.513533/