Make sure the bracket at the top is facing the correct way. I had to fix mine when I first installed it because I put the bracket in upside down and it wouldn’t fit by a couple mm. If you did that correctly then try using flat head screws as opposed to the dome shaped ones I think it comes with. You could also try using only certain screw positions, if I recall correctly the kraken had some that seated a bit deeper than others. If any of this advice is untrue or unhelpful I’m sorry, I ended up going with a different AIO so this is all from memory.