Help with new build

[JD0107]

hello

I just finished my first time building a pc buuut it won't power on. A small red light will blip on for a split second on the motherboard, but that's it. I followed along with a video (so I tried retracing my steps) plus the manuals, and I don't think I forgot something? I rechecked all the cables were plugged in.. Obviously I did something wrong.

MB- MSI x570 gaming plus
CPU- Ryzen 7 3700
GPU- geforce rtx 2060
Crucial m.2 ssd 1T
Ram- Corsair Vengeance
PS- I'm using the 600w from my old pc while waiting for my new 650. I would have waited, but it hasn't even given me a shipping date and I have no patience. Mistake? Possibly. Headache? Definitely.

I feel like I forgot something. I used PC part picker for compatibility, but who knows.

Help?

- - - Updated - - -

Let me see if I can add a picture or two... sorry for quality.


https://imgur.com/a/0vJwX0g

[Temp name]

Make sure the power button is attached to the right place. Front-panel headers are annoying, it's easy to plug in wrong, and practically impossible to see in pictures unless you can read the text on them.

Pull out all the PSU cables, then put them back in, then try booting. It's possible there's a loose connection (especially care for the 24pin and 8pin for CPU)
Try pulling out the GPU and see if it still happens.
Try pulling out each stick of RAM 1 at a time and see if it still happens.
Try plugging the PSU back into the old computer and see if it still works.
Try using the new GPU in the old system (if the problem persisted through just pulling it out).
Try using new RAM in old system, if it fits (if problem persisted).