Check for Hyper M.2 X16 card in PCIEX16_2 port on ASUS B550-PLUS.
Check for Hyper M.2 X16 card in PCIEX16_2 port on ASUS B550-PLUS.
You're facing a common compatibility issue with your motherboard and SSD configuration. The problem likely stems from the mismatch between the PCIe slot type and the SSD specifications. Your setup uses a 16x Gen 4 slot (Hyper M.2 X16) but the SSDs you installed are Gen 3 devices, which aren't supported by that slot. Additionally, the motherboard manual indicates it's a full-size slot, yet only 4x Gen 3 support is listed—this inconsistency can prevent proper detection. Trying to force 4x Gen 3 NVMe cards into a 16x Gen 4 slot will cause detection failures. Consider using a compatible 16x Gen 4 slot or upgrading to a 4x Gen 4 slot if possible.
The card functions as a physical adapter and doesn't perform lane switching, which means you're restricted to the supported M.2 slots. You should see one M.2 SSD detected. If not, the slots are misaligned. Try swapping them to the opposite positions. Inserting it into the main slot will likely activate all four drives. You didn't require a GPU, right? Check the support page for details: https://www.asus.com/support/faq/1037507/. If not available, search for another adapter that supports PCIe switching. These are typically hard to find now and were once costly. You might also want to upgrade to larger-capacity drives instead.
A more affordable option is a card featuring an integrated PLX switch.