I got a new case after my old case was rusting (9 year old case lol) and after putting everything in it didn't post. I thought it was the GPU because the debug lights on my MSI B350M Gaming PRO said it was such, but it turned out to be my CPU (Ryzen 5 2600).
Now it turned out that somehow I got a tidbit of thermal paste onto the pins of the CPU, this was cleaned out using a toothbrush and isopropyl alcohol.
After slapping the now clean CPU in and putting my AIO onto it my pc posted and booted to Windows...But with one of my ram sticks being reserved for system. Thinking it was odd I swapped the ram sticks around to see if that would do it, still only one stick. Trying to find what stick it was I booted with only one stick installed, it booted with stick A in, then it didn't post with stick B, I put stick A in and booted to bios thinking that I should go ahead and update bios when I was already working on my pc. I flashed it and it booted just fine. My father thought that maybe with the new bios the other stick may work (okay I'll trust you, you are the head of IT at your work idk), after putting stick B along with stick A in, my pc didn't post. My board doesn't show any debug leds and can sit there with fans ramped up for 30min on end without posting. I've swapped the sticks around and tried with only one in, the Bios looked different from the other one that I had (had "MSI Click BIOS 5" from around 2018 and went to 7A39v2NR). I'ved tried clearing CMOS to no avail.
This all is really odd to me because I didn't even remove the RAM from the board when swapping cases (idk what the hell happened with the CPU, I had my dad install the AIO when I was away).
Motherboard: MSI B350M Gaming PRO
CPU: Ryzen 5 2600 OC 4.20Ghz
GPU: Zotac GTX 1060 6gb AMP Edition
PSU: EVGA 500W
RAM:  Ballistix 2666MHz 8gb
New Case: Cooler Master Q300L
Old Case: Unknown
Would love any input on how I could try and fix this.