Hi,
1. make sure you use the correct suite of actions. If you use 2D physics, e.g. rigidbody2d, collider2d etc, you also need to use physics actions with 2d at the end. The standard (3d) variant is without the suffix.
2. For debug purposes, add a state with key down that also leads to the particle firing state, when pressed, so you can quickly test it and tweak it. If it works well, you can add complexity and trigger it with a collider. Generally, try a partial solution first.
3. The easiest implementation is a single state, and a global system event called OnTriggerEnter (2d). When you add that to another state, and run into the trigger, it should activate. But it has no options. If you want options, you can use the trigger actions.
4. Make sure that the collider is set to trigger.
5. To fire particles, you need “particle” actions from the Ecosystem (free PM addon). I am quite sure I got them there.