my rig does not boot up

The motherboard doesn’t boot up when I connect the Riser.

I have connected only 1 RTX 3070, ignore other cards that are not connected.

My issue is with the motherboard that doesn’t boot up if the GPU is connected through Risers. If I connect the GPU directly to the Motherboard, it will work.

I’m using a 6+2 PCI Splitter to connect the Riser and the GPU. See the video for more.

Any idea why the motherboard doesn’t work and I think all cables are connected correctly unless the cables are bad? But, I have tested several cables and risers, still the same.