Exit portal pitch black halp!

[CTZn]

Then normally portals should work, provided that:

1- they are in effect exported as portals, not ordinary meshes
2- their normals are pointing into the interior of the room. Either flip their normals or turn them around.

Note also that exit portals must be single surfaces (ideally two triangles per portal), not volumes as real glass panes for instance.

If this doesn't work either for you, just create a new scene with an empty room and one opening with one portal and one of the env lights (sun preferably). If it doesn't work still then please link us to that test scene, as skp preferably. SketchUp users should help you better than me then.