Doesn't z590 have 20 PCIe 4.0 lanes? That's 4 for the M2 SSD, and 16 for the GPU card. You should be able to use both at the same time, and get 16x on the GPU - right?
I too have a z 590e motherboard the second slot not read with a 980pro 4 0. I9-11900k. Wii the bios correct this problem.
Just got a new Strix Z590-E Gaming Wifi board. Installed an i9-10850k. 4 M.2 slots. M2_1 slot is disabled for 10th Gen. Only works with 11th Gen. Installed working NVMe drive in M2_2 slot but not detected. Tried M2_3 and M2_4 slots and it works fine. Tried 2 seperate NVMe drives.
I'm not sure if I have a bad board or there is some setting in the bios. Nothing I can find.