Yes, you can install a 1x PCIe card into a 16x or 4x PCIe slot

why its not doing it in the x4 slot is the card will be pulling less power as its basically bottlenecked by only getting 14 the data sent to it

Have you ever thought if you can plug PCI Express cards into x16 lane slot? In this video

canyon slot Have you also tried to put your video card in second long PCIe slot? Does the card show as x8 when you do that? If yes

can you put a gen 4 ssd in a gen 3 slot 2 devices are x4 or less lanes PCIe devices Don't matter if the adapter PCB physically fits a x4x8x16 slot, the is and always will be x4