No post/cpu debug light((Mobo issue?))

[ScharkBait11]

TLDR: tried to go to itx board  //used 2 cpus no avail  /lights and fans on running but cpu light on no post

R 9 3900x///spare/// r 5  2600x both confirmed working(post)  in b350 board
Mobo — b350f  going to b450I
Same ram 4x8gb crucial (using one for testing) 
Rtx 3070 

Okay so I was trying to downsize from a rog strix b350 f motherboard to a rig strix b450i to put ina smaller case

I get  red cpu light on b450 mobo with with 3900x  so I tried 2600x  same thing
Cpu fan spinning 
Gpu fans spin at star then stop after a bit 
Rgb Lights on motherboard  are on

So I took both cpus tried in b350 
Ram one stick
And 3070

And worked fine..

Am I missing something or???

I looked to  see about bios updated says 2600x compatible from 0207 update and the lowest the website has is 05** and it description says first update .

Idk if I been looking at this too long or what? 
Any help appreciated.

 

[Sjaakie]

Sounds like a motherboard issue indeed. DId you already reset the CMOS?