There may be a chassis intrusion option in the bios, make sure it is disabled if there is one. Or it is probably an electrical short somewhere
Can you enter bios? if not maybe an electrical short and you will have to double check the block mounting, does it make contact with the case from behind, or the mono block LED connection
I have a very expensive case that a RV 10 edition just would not work in because the armor on the back of the board made contact somewhere, the case standoff's are just very short
Fortunately it did not damage the board