NVME drive not working in second slot of Asrock B450

2 slot does not share bandwidth or conflict with SATA ports That is clearly untrue I have a non-MSI board it has slots and 10 SATA slots

The number of direct connections available by a PCIe slot or card is represented by the size NVMe SSDs require 4 PCIe lanes to operate PCIe x1: a single

pcie 8x slot pcie is about 4x faster The add in cards plugged into a X4-X16 pcie slot will have some sort of adapter

pcie slot for gpu 2 M key slot is compatible with both B+M key SSD and M key SSD The last but not least, you should check whether the slot supports PCIe (