ASRock Specs on your Motherboard is a little bit confusing since it says it does support PCIe Gen 3 x4 for Picasso processors but then says that Athlon APU's support only Gen3 x2: ASRock > A320M-HDV R4.0
So going by ASRock Specs Athlon series APU seems to be compatible with only GEN3 x2 speeds.
I would check the NVME Support to see if your SSD can be used on GEN3x2 slot.
Here is ASRock QVL List for Storage devices for your motherboard. It shows both Gen3x4 and Gen3x2 Storage devices plus SATA: ASRock > A320M-HDV R4.0
There are 4 or 5 more GEN3x2 devices further down this list.
EDIT: You can use a GEN3x4 SSD on a GEN3x2 port because it is backward compatible but it will run at GEN3x2 speeds and not GEN3x4 speeds: