I just put together a new build with some old and some new parts, but some really weird stuff is happening and I can't figure out what.

Specs (new parts):

Case - Cooler Master Masterbox MB520 RGB

MB - AsRock B450M Pro4

CPU - AMD Ryzen 2700x with stock cooler

PSU - Cooler Master MasterWatt 550W

Storage - Crucial P1 M.2 500GB

(old parts)

RAM - Corsair vengeance 4 x 4GB - 2133 MHz

GPU - AMD R9 380x

The first time I made this build I also used an old Corsair VS550 PSU, but it never even got a beep so it was broken from the get-go. After switching out the PSU it does beep and when I press the power button everything turns on except the GPU. Instead, it just ticks once every second, as if it tries to start up but can't. This same thing is happening with the CPU fan while it's spinning. Every second or so there's a tick and it slows down for a split second. This also happens after removing the GPU. I even recorded the sound, in case anyone wants to hear it.

After about 10-30 seconds it shuts down and restarts immediately, without ever reaching the BIOS screen. Even when shutting down manually with the power button it restarts. I first removed the RAM and tried different sticks in every slot, but the results were the same. Even without any RAM it keeps looping.

At this point I read it might be the CPU that's overheating, but another weird thing is making me think it isn't. When I press the reset button on the case, the CPU fan either comes to a stop or speeds up to maximum. What happens when I press it is completely random. When I keep the reset button down and the CPU fan spins at full speed for more time than it takes to shut down and reset, everything keeps working. Even after letting it return to normal speed. However, even when this happens, I can't get any visual output. Not from the GPU or from the internal graphics.

Now, because I've been struggling with it for a while, I've removed and rebuilt everything a couple of times. One time I bent 2 pins on the CPU, but I bent them back and everything seemed to be fine again. I've cleaned the CPU cooler and put new thermal paste on it. I've reconnected the wires for the power and reset button a couple of times, but I'm certain they're on the right pins. The weird reset button/cooler interaction doesn't make any sense to me.

I'd be really happy if anyeone had any idea of what might be wrong. Everything I've read about doesn't show all of these symptoms and is either solved by stuff I've already done or by just buying a new... everything.

Thanks in advance.