Thanks! So you think my issue is the risers right? How can i check if the issue is actually the risers? Should I remove all GPU and connect one by one and see which one detects and which one doesn't?
I use 6-pin PCI-E risers. Three thicker wires that are designed to spread a higher 12V load instead of two used by molex and sata connectors. The 6-pin risers also use four capacitors for a more stable current flow compared to the three used by the molex and sata risers. The good ones also come with a voltage regulator to prevent spikes. The problem is they are sold out everywhere, so you have to order them from China which can take 2-3 weeks. That's why it's a good idea to order twice as many risers as you think you will need. Nothing worse that having cards idle while you wait for risers.
https://www.aliexpress.com/item/TISHRIC-VER006C-Blue-PCI-E-Extender-1x-to-16x-PCI-Express-Riser-Card-60cm-USB-3/32808611545.htmlI don't recommend using unpowered risers. PCI-E 3.0 cards tend to draw more power from the slot and the ribbon cable wires are too thin to use under constant load.