no POST with SSD installed in PCIe slot

PCIEx16 drops to x 8 when M2 SSD is installed??? can i use m 2 pcie 4 0 in 3 0 slot PCIe buses can support 1x, 4x, 8x, and 16x lanes PCIe has an effective transfer speed of up to 985 MBs per lane which means there is a potential transfer can you put a pcie x1 in a x16 slot disk I updated the BIOS; installed Linux on it and it works without a problem, so it could not be a hardware issue I'm not sure if

can i put a gen 4 m2 in a gen 3 slot For example, most SSDs come in the NVMe form factor, which means they only have access to four lanes At PCIe speeds, that's 8GBs of constant data