if the vray physical camera is on and less value for your rectangular light. you wont really see them. physical camera works together hand in hand with the the vray sun. if you are using night scene better to turn off the physical camera. all lights (omni or point lights, emmisive and rectangular lights will appear)
if you insist in using the camera try lowering your fstop value, decresing the shuterss speed or even makign your ISO higher, but lo be careful because if your using ISO more than 800, the image will become noisier.