When I change the Source Cubemap Angle, nothing visually changes. Likewise if I change the Cubemapped image itself (ie - load in a new one), nothing changes, still stays the same and shows the old one…
BUT - then if I close out level and re-open, then it is changed (angle, chosen loaded image). Like it requires shutting down UE4 and re-opening to see the results.
The only thing I can change realtime is Brightness.