So, @suthriel appeared to solve your problem. I have a question for suthriel, though, about those three resolutions when importing a cubemap for HDRI.
If the slider stays at 2048, is it because the texture’s Imported Value, which is 4096 x 2048, where 2048 is the second value in the res? or is it because of the original texture having a resolution of 2048, or rather, that it was rendered / saved at a 2048 resolution before import? I know it kinda sounds like the same question or the same answer could be derived from either question, but what I’m asking is if the initial resolution before import of the cubemap is becoming a limit in Max In-Game Res in Unreal?