Solved Suspect my new AMD 7800xt Hellhound might be faulty

Hi guys,

I just upgraded from a GTX 1070ti to a "PowerColor Radeon RX 7800 XT Hellhound OC 16GB". For some reason i cant get my pc to boot with my new 7800xt plugged in. When i turn my pc on, all the lights and fans on the gpu turn on, but my motherboard just shows the VGA light and doesnt move past that.

Ive tried all 3 PCIE slots, ive tried a different HDMI cable, Ive tried different psu cords.
I've also tried booting with both the 1070 and 4800 plugged in (with my monitor plugged into the 1070) and im able to boot, login and download AMD's software where it detects a 7800xt and downloads drivers. but when i boot with just the 7800xt it doesnt move past the VGA light.

But when i swap back to my 1070ti it boots fine - even without drivers


Im out of ideas and i think maybe ive got a faulty card - is there any bios settings or software/updates stopping it from booting maybe?
Stores are closed over the weekend so I have time to test.

My specs are
AMD Ryzen 5 7600X Processor
Gigabyte B650 Gaming X AX DDR5 Motherboard
Thermaltake Platinum 750W Modular Power Supply
Kingston Fury Beast 32GB (2x16GM) DDR5 Ram
Windows10
2x 1080p monitors - 1x HDMI 1x DVI cable

Thank you.

Problem solved. it was my riser cable - its a gen3 riser cable, when my pcie slots are gen4's. i had to shift my radiator to fit the gpu without a riser cable but it works.