There’s a few different things that could be happening here…
Did you change any other setting in your emitter? It should work by itself by just changing the material.
Did you test it in the level? It’s possible the sprites are “hidden”/invisible in the editor because of camera angle (lit sprites tend to look pitch black if you look at them from bellow) or bad zoom/scene placement (being zoomed too far can easilly make the camera go through the sprites and make them very hard to see.) I know it sounds kind of dumb but it’s just sooooo easy to accidentlayy misalign your emitter in the viewport and it can be really hard to recenter it again when it happens!