My Players see a black screen

I purchased Tomb of Annihilation and am playing it with my group. We are all new to Roll20. This may be a dumb question but when I move the player bookmark to Port Nyanzaru they see everything just fine. But when i move it to say Firefinger or the Merchent Palace they see nothing but a black screen. Even if i try to remove the fog of war. What am I missing? Please help. 

Sounds like you have  dynamic lighting enabled.

Thank you. That seems to have worked.