'Device Failure' pop up means nothing without a pic of the pop up.
Did you use DDU to remove all traces of Nv drivers/software before installing the 6700xt.
And what make/model is your really old PSU ?
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..