I recently bought a used MSI Aero RTX 2080 8GB that came with an AiO mount so I mounted a 240mm AiO to it (not that I think this is relevant because the GPU isn't even on long enough for heat to be a problem.
When I go to boot up the PC, at first it didn't show anything at all, so I though oh great it's a dud I got ripped off lol. But then I went to Best Buy and bought a new RX580 to run some tests on (since I have a Ryzen 7 3700x which doesn't have an iGPU).
I put the RX580 in an still nothing, so I thought oh even better my whole system is broken now. But then I remembered about CMOS and decided to clear it out by removing the battery and all that (also the battery is still out until I get it up and running). And hooray the RX580 boots into Windows. So then I powered down and tried the RTX 2080, and hazah!... it POSTed, but only for 10 seconds then it blanked out.
Ok so then I used the RX580 to boot into Windows ran DDU in safe mode and cleaned out all old drivers. Tried the RTX 2080 again and still same thing will boot into BIOS and then cut all display after about 10-20 seconds. I stay in BIOS and never even boot into Windows to make sure it's not a driver thing and still it cuts display. I tried both my PCI-e slots, every DisplayPort (4) and HDMI port (1). Still the same result. I updated my BIOS to latest (July 2020 version) and still same result.
Parts in System Build
MOBO: ASUS Prime B350-Plus
CPU: Ryzen 7 3700x
RAM: Corsair Vengeance RGB Pro DDR4-3200 CL16 (2x16GB)
GPU: RX580 or RTX 2080 MSI Aero 8GB
SSD: Samsung 970 EVO 250GB
PSU: Corsair CX750M
https://pcpartpicker.com/list/gKg3Gc
Any help would be greatly appreciated!
Edit: fixed PC Part Picker link