How to cast static shadow for sprites

Hi,
I am trying to add sprites on a 3D level. Actually, I am using Maksedlitsprite as sprites texture. There is the thing, sprites can only cast shadows when I turn on the dynamic shadow, but the static shadow does not work.
Besides, it is always dark on the side that does not receive light, but I hope that the color should be a little bit bright.
I am still a freshman, could you help me?
Thanks for your reply!