Question Changed PSU and GPU now USB and HDMI dont have any output

[ShadowMellow]

Hey, I know this question got asked a lot but I'm trying to help a friend (they're pretty new to PC building) upgrade their GPU and PSU remotely but we need some advice.
Basically after connecting everything to the new PSU, the Motherboard would indicate it's on and all fans would start but there is no HDMI output and the USB mouse only blinks once before dying. We replaced all the cables with the new ones and connected them correctly and firmly as far as I can tell and we already tried to reset the BIOS by removing the CMOS battery but that showed no change. Monitor and mouse are all working and everything had worked fine right before we replaced the GPU and PSU so I'm really at my wits end here, we tried a lot from other threads in this forum but none of it has worked so far.

Our Specs are:
Motherboard: ASUS PRIME A320M-K
CPU: AMD AM4 Ryzen 5 3600 6x
PSU: Thermaltake Toughpower GF1
GPU: Gainward GeForce RTX 3060 GHOST
RAM: 2x Crucial 8gb

Update: It turned out the CPU 4x4pin was being fussy and wanted to be pushed in a .0001mm more before it wanted to supply power.... Everything worked fine afterwards and now I just feel like an idiot.

 

[helpstar]

please take some pictures to be sure all is connected well, upload to imgur.com and post the links

most common problem is that new PSUs have a splitted ATX main power cable on the PSU´s side. Is the 18pin main plug + underneath of it the 10pin plug connected to the power supply?
AS well as the 8pin ATX12V plug to the PSU?

 

[ShadowMellow]

Okay, this is gonna sound incredibly stupid but we were unplugging and replugging all the power cables for the 30th time and figured we might as well reinstall the ram sticks since we had a similar issue before that was caused by them. My friend got really pissed off that the CPU 4+4 pin cable kept getting in the way so she pressed it down into the mother board while the PSU was on and Lo and Behold it suddenly boots!

So apparently we really did have everything plugged in right, the 4pin was just sliiiiightly not plugged in enough even though it clicked and everything. After that the PC booted and we could install the GPU no problem, it was really just that one cable that wanted to be pushed around I guess.

Thank you for the help though! It all worked out but I just feel incredibly frustrated and silly now.