PC doesn't boot after PSU replacement

[Cubiss]

Hi all,
today I tried to upgrade my PC, replacing PSU (Seasonic SS-620GB for Gigabyte P850W) and adding a HDD. After turning the PSU on only motherboard LED strip and power light turn on and hard drives start spinning. None of the diagnostic LEDs light up (Asus Q-LED, when LED is on, there is an issue with device). None of the fans start spinning (CPU/GPU/Case)

What could be the cause of this? I'm gonna do some more troubleshooting now but it's worth a shot checking if someone else came across this issue.

Specs:
Motherboard: ASUS PRIME B550-PLUS

CPU:              AMD Ryzen 5 3600

GPU:              Gigabyte RX 5700 XT GAMING
PSU:               Gigabyte P850W
RAM:              Patriot Viper 4 Blackout Series (4x 8GB stick)
SSD:               Samsung 970 EVO 500GB
HDD:              Seagate BarraCuda 1TB
                       Seagate IronWolf 4TB CMR
 

[PDifolco]

I'd say your 24pin Mobo connector isn't fully plugged one side or the other

[Cubiss]

20 minutes ago, PDifolco said:

I'd say your 24pin Mobo connector isn't fully plugged one side or the other

This was indeed the issue. This is my first time using fully modular PSU and the 24 pin has 2 PSU side connectors which confused me a bit Thanks for your help.

[zyzz84]

did you use the cables that came with the new psu or the old one? because you always want to make sure you use the ones that come with the psu

[CommanderAlex]

32 minutes ago, zyzz84 said:

did you use the cables that came with the new psu or the old one? because you always want to make sure you use the ones that come with the psu

Can totally agree here on this one. I've read horror stories of those on these forums that did not change out the cables and took out components in their PC for the sake of saving time and cable management. 

 

You can ONLY use the same cables if their from the same family/brand of PSUs. Corsair, I know, has a chart for this so always consult outside information before using cables from another PSU. 

[Cubiss]

The old PSU wasn't modular so I definitely used the new ones The issue was that I only plugged half of the 24 pin (there are 18pin and 10 pin connectors on PSU side, I didn't plug the 10 pin).

 

Everything works fine now.