[Newbie] Particle System does not work right.

I am trying to create bullets. I’m recreating the Survival Shooter Extended version. When I play the game, the bullets becomes a pink square. I then placed a material under Renderer but now it doesn’t display/render anything. Also, I tried using other materials that I used within the project but still renders nothing.

What shader is on your bullet material? What cameras are rendering? Are the particles behind anything?