Are you using two separate 8 pin pcie cables from psu to card, and did you use DDU to remove all traces of Nv card drivers/software?
Ryzen 5 5600x, B550 aorus pro ac, Hyper 212 black, 2 x 16gb F4-3600c16dgtzn kit, NM790 2TB, Nitro+RX6900XT, RM850, Win.10 Pro., LC27G55T..