Why aren't some of my lights working?

I am working on a 2D-sidescrolling platformer, and while working, I have found that every point light or spot light I added after the 3rd one was finished does not work correctly. That is to say that the lighting effect does not show up. All my lights, both working and not, have a Z-index of -0.5 while everything else but the Camera has a Z-index of 0. All the values and specifications for their lighting is the same as the first working three lights. Is there something I am missing or don’t know about? Is there some manner of limit to the lights I can work with in 2D space?

I guess that you are working in forward rendering, and/or your dynamic lights are set to 3. (Quality tab, rendering section, per pixel lights count.)
Also try to set the lights that you want to be affecting the objects all the time as important in their properties.