Precision 7550 GPU upgrade to RTX 5000

I have a 7550 with 10850H CPU and a T2000 GPU.

I want to upgrade the GPU to a RTX5000. I bought the card (N19E-Q5-A1), and also a new heatsink (VP4F7), but after replacing the old components, the laptop "blinks" for a sec, fans are working, and then it shuts down.

After disconnecting the new GPU (both MB connectors, and power cable) I can start the laptop and I get an M1004 error.

According to my search this indicates an overheating problem, but after a couple of tries, and checking the paste, and the thermal pads, it seems to be okay, it should have a good contact with the heatsink, but I'm still getting the same error.

So my question:

a) did I missed something which should be replaced, and what that would be

b) or the card is simply malfunctioning? If yes, is there some other way to verify that?

Thanks