I don't have an answer but am experiencing a similar issue. This is my first time using Playmaker so I thought I might be doing something wrong.
1. Created a 2D sprite object with a 2d box collider and 2d rigidbody
2. Created a 3D cube, got rid of the box collider and gave it a 2d box collider with trigger ticked. Unticked mesh so it was invisible.
3. Created an FSM on #2 for on trigger enter 2d
4. Also created another 2d sprite, added a box collider with trigger ticked then setup an fsm using on collision enter 2d
Neither of them trigger when the character passes them. They're on the same level and I've tried giving them tags all without success.
Any help would be appreciated
Sorry for tacking onto your question but I thought it was better than starting a new one