Your size is way to small. He has .0299ft which is .00911M. You could also just type 0.0299′ or 0.0299ft in the field and blender will convert it to meters for you. Also textured lights only work in cycles. Also sometimes there are problems with some GPUs. try switching to cpu. It also could be because of some major bugs that where in 4.0.1. You might need to update to 4.0.2
