Question Dell G5 5090 not turning on

[RetroGameReaper]

Since yesterday, my PC hasn't powered on. It's a Dell G5 5090 desktop that I've had for two-ish years now. It was working fine the night before and then I turned it off to put an SSD in it (which I decided that I could do without), and never turned it back on once I put it back. When I plug it in, the PSU clicks, lights up, and the fan starts but only for a second and turns back off instead of staying on for few seconds more. Nothing happens when I press the power button. I tried just about everything from Dell's support page. Hopefully someone can help me out with this because I really need my computer this weekend for some personal stuff.

 

[Lutfij]

Welcome to the forums, newcomer!

iI tried just about everything from Dell's support page.
Could you share what you're tried, so we're not repeating what hasn't worked for you...?

Also, did you tinker with any innards in the prebuild? Perhaps try and reconnect the power cables from the PSU to the motherboard. As for your prebuilt, what discrete GPU are you working with? From what I'm seeing using Google image searches, that motherboard has proprietary power connectors meaning the PSU is somewhat bespoke so off the shelf PSU's are going to be nearly impossible to work with and to troubleshoot your platform in case the PSU is the real culprit. If you're handy with a multimeter and you can identify the pinouts on the PSU/board, you could fabricate a harness for it though this thread would indicate that you're not adept with the pinouts on a PSU/motherboard.

 

[RetroGameReaper]

Update: I isolated the GPU and figured out that its the problem but I don't know why. When it's connected to the power supply, it works, but once it's installed in the computer it doesn't work.

Here are some videos of what happens:

https://imgur.com/a/VlvDsLi

View: https://imgur.com/a/VlvDsLi