Video card is good but only 2 led on

Hello guys,

I have an iMac 2011 A1312 which video card is failed and I replaced with Radeon WX4150 ready to use from seller. it runs fine at first, but when I install mac os it always dead on half progress. then I tried to use the video card on my 21 inch core i3 imac and it's fine. installed big sur with no problem. but when I use it on my A1312 imac, only 2 led on. fan running but like no activity. I clean video card slot but no luck. am I damage something on the board?