I had already done all of the things you guys suggested but I found the answer. The way I had modeled my walls was with only one layer of surfaces but I had made the material used for them two sided. So basically the directional light had to compute an entirely lit surface on one side and an entirely unlit surface on the other side, resulting in the unlit side being completely black. Once I wrapped the building with the external layer of the walls and ceilings, the inside was lit well. I guess unreal can’t compute the directional lighting on a surface with a two sided material when the photons only hit one side (even with windows with light portals).