Question PC will boot up when using ryzen CPU, but not athlon 240

[harkins.tiger]

So I am in the midst of building my friend a computer, using an RX 570, an athlon 240ge, and 8GB of ram, on an asrock b450 hdv r4.0 mobo. however, we couldnt get a post when we powered it on. I have verified that the all of the parts in the system worked, by switching out the athlon for my ryzen 5 1600, and put his athlon into my system. both systems booted with each others CPU's, so I assumed that the b450 board must have had an old bios that did not support the athlons. however, once I updated the bios to the latest version and returned the athlon to its original motherboard, there is still no signal from the monitor. please help.

 

[AllanGH]

All BIOS versions on the Asrock B450 HDV r4.0 motherboard support the Athlon 240GE processor, according to the manufacturer.

Pull the GPU and check it using the iGPU?

 

[harkins.tiger]

All BIOS versions on the Asrock B450 HDV r4.0 motherboard support the Athlon 240GE processor, according to the manufacturer.

Pull the GPU and check it using the iGPU?

already done. neither the dGPU nor iGPU send any signal to the monitor, despite when a ryzen 5 1600 was used with the same dGPU the signal was perfectly fine.

 

[AllanGH]

You may have already done these as well and, if so, I apologize...
Check the GPU manufacturer's website for any issues specific to the combination of the RX 570 and the Athlon 240GE processor.
If you don't see anything of concern then.
Pull the system down and breadboard it...and try again.
If no joy, then try a CMOS clear.
Still no luck, then reflash the BIOS.