[SOLVED] No POST. Mobo signifies CPU problem but CPU fine. Tried everything.

Apr 4, 2020
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AMD 3800X. MSI B450 Tomahawk MAX. GTX 960. 8gb of Corsair RAM. When the PC is started there is no post. The motherboard EZ Debug CPU led lights up to signify a CPU problem. The CPU is not damaged as I've swapped it with an AMD 3700X and the problem has remained. The motherboard is also not damaged as I have swapped it with an ASUS ROG STRIX B450 and the problem has remained. I was thinking the BIOS wasn't updated to support AMD's 3000 series but I know that the MAX versions of the board always ship 3000 series ready. Never the less, I tried using the flash BIOS feature and when used the red LED on the back of the board is meant to flash to signify that the BIOS is being updated. It doesn't flash although using the button does turn the entire PC on. I'm thinking the motherboard won't update to the latest BIOS in the USB stick because it's already running that version. I'm completely stumped, as the motherboard says the CPU is at fault when I know for a fact it isn't. Unless it's the BIOS, in which case what am I doing wrong when updating it.
 
Apr 4, 2020
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I am a bit confused.

Just to clarify.
The Tomahawk shows CPU LED with either CPU?
The ROG does what when you install each CPU into it? (It would theoretically need a BIOS update for either of those chips)
Yes. Both CPU's show the light and it's shown on BOTH boards. The ROG would need a BIOS update but the tomahawk is a MAX so theoretically should already have the correct BIOS in. That's why I'm so confused.