Question New motherboards, red CPU light, no beep. Old motherboard still boots.

[Cherokee0621]

I switched from an MSI B450 Tomahawk Max motherboard to an MSI X470 Gaming Plus Max that I received in a trade. CPU light comes on, no beep, no display. The normal stuff.
In frustration, I went out and purchased an MSI MPG B550 Gaming Plus, which to my dismay has the same problem. I switched all of my components to a completely separate case, and it was able to boot up normally. I can’t keep it on long though, as there’s not enough airflow to keep my CPU cool.
Even more frustrated, I switched everything back over to my original case, with my B450 as the motherboard. It booted right up. I swapped it out again for the B550, and I’m back to where I was with only the little white CPU light on display.
I’m pretty baffled at the fact that it’s refusing to cooperate with me, and I could use any help possible. I have a flash drive that’s ready to flash the bios, and I tried unsuccessfully, not to my surprise.
I’ll switch back to my B450 for the time being, so I’m not without a computer.

CPU: AMD Ryzen 9 5950X
GPU: AMD Radeon RX 6900 XT Red Devil
PSU: EVGA SuperNOVA 850 GA
RAM: (2x8GB) Corsair Vengeance LPX, (2x8GB) G.SKILL Ripjaws V

 

[Cherokee0621]

I’ll clarify that the B550 was able to boot up in my smaller case, but not my normal one. There’s no difference in wiring, aside from the fan setup. The problem is, my CPU was getting to the 80°C mark, when it’s normally around 55°C in my regular case. I didn’t want to risk it.
Edit: I’m now back to my B450, and booted up properly. I have to go to work, but I’ll try any remedies once I’m off.