HDR Keeps Disabling

Hello!

I love this frickin game. I can't get enough. I'm trying a new play through of Frackin' Universe and my HDR keeps toggling off. I haven't had this issue with other games, and when I was playing just last week it worked with HDR in windowed mode at least - also with the same mod enabled. I can' t figure it out and it's driving me batty. Has anyone had this problem or know of a fix?

Thanks!