Question PC doesn't boot upon pressing power switch but flashes during PSU power on - Is it RAM, Mobo or PSU ?

[AdLibTact]

System
Mobo: B650M Aorus Elite AX v1.3
CPU: Ryzen 7 7700X
GPU: 1660 Ti
RAM: G.Skill Aegis 2 x 16GB (max 6000Mhz)
AIO: Thermalright Frozen Prism 360
Case: Montech Air 903

Installed Windows 10 Pro fine, activated EXPO profile 1 fine, didn't OC anything or touch any other bios settings.

3-day old rig was working fine 2 nights ago. I wanted to add a SATA SSD & a HDD so I connected them to the SATA ports. Mobo didn't light up (+ no post). I disconnected them, then mobo lit up with red DRAM light & "no signal" on monitor.

I reseated RAM & GPU, red DRAM & No Signal continues.

This morning, I took out ram, used eraser to rub the RAM & GPU inserts & used thin brush to ensure contact surfaces are clean.
Now the mobo doesn't even light up...

I ended up uninstalling everything from the case, & reinstalling everything to ensure all connections are correct & properly inserted.

I followed the stickied thread's instructions on everything, e.g. careful seating, connectors, GPU to monitor, flashed bios (no components, just mobo & cpu power connectors), extracted cmos battery + jumped cmos pins (always psu unplugged, both as an empty board, and with only cpu & AIO connected) etc.

Also tried solutions from YT like unplugging PSU & clicking pw sw for 30s, trying both ram sticks on each slot 1 at a time.

Did barebones set-up - CPU, CPU cooler, 1 ram stick & GPU (no iGPU), clicked switch (also tried jumping w screwdriver).
0 response from mobo despite flashing during PSU power-on

Have spent 20+ hours over past 2 days, would appreciate any help from anyone who has fixed this problem!

 

[rgd1101]

brand and model of the psu?

 

[AdLibTact]

brand and model of the psu?

Antec EAG 650W PRO Modular (Mobo, cpu & gpu power cords are attached to psu) I installed the 2 extra SATA drives (1 HDD 1 SSD) with 1 accessory drive power connector (so 1 connector for both drives) that can be added onto the back of the PSU). I searched 2 wattage calculators sites & both told me i'd need 450-500W, so i'd be extremely confused if it shorted my psu .-.

 

[JayGau]

Used an eraser to rub the ram and gpu connectors? Why did you do that? I understand you are desperate but this could have done way worse than good. The eraser can damage the gold plating on the connectors.

Your post is a little confusing and it's hard to know what the current state is. What does "0 response from mobo despite flashing" mean? Are the fans start spinning when you turn on the pc? Is the Prism 360 RGB light up? Maybe a video of what happens could help people here to figure out what is going on.