Motherboard is an MSI X470 Gaming Pro... it has the CPU 8 pin and 4 Pin P4 (CPU2) power connectors.  The EVGA 600 series white only has the 8 pin CPU-1 power.  The last time I built a PC a year ago the power supplies came with ATX12 8 pin and the 4 pin.  Now it seems quite a few PSUs only have the 8 pin??
 
Just built a new system with Ryzen 3600 and it switches on and lights up but does not post.  I have read that the additional ATX12 4 pin on a motherboard is only required for extreme overclocks?
 
Assuming these motherboards will boot with the CPU2 4 pin socket not connected... then perhaps the bios needs to be updated to be compatible with ryzen 3600.
 

I do not see any @ < £50 UK pounds

Cool GTX
I do not see any @ < £50 UK pounds

Don't worry about that price... motherboards should be without the ATX12 4 pin connected according to what I'm reading.

Looks like you're going to have to go up to at least 750w bronze to get 2 EPS cables, personally I don't use anything less than platinum and wouldn't recommend anything  
 
less than gold. Just isn't worth it IMO.

This looks to be the entry price: [Currently In Stock on EVGA EU site]

EVGA 650 GQ, 80+ GOLD 650W, Semi Modular, EVGA ECO Mode, 5 Year Warranty, Power Supply 210-GQ-0650-V3 (UK)
 
Looking under the tab marked "Specs"
EPS (CPU) 2x 8pin (4+4)
92% (220VAC~240VAC) efficiency or higher under typical loads
---------------------
The Best on on the 650 list: 94% (220VAC~240VAC) efficiency or higher under typical loads

EVGA SuperNOVA 650 P2, 80+ PLATINUM 650W , Fully Modular, EVGA ECO Mode, 10 Year Warranty , Includes FREE Power On Self Tester Power Supply 220-P2-0650-X3 (UK)
 
 

It should work with only CPU_PWR1 (8-pin) connected..CPU_PWR2 (4-pin) is power for increased overclocking potential.
 
BIOS version 7B79v1A adds support for Ryzen 3000 series CPUs..You need that one or newer and almost certainly guaranteed that's what the problem is..There have been 8 other BIOS updates, not counting the original, prior to that one..I'm pretty sure your board just has one of the older BIOS versions.

See: How to flash the BIOS
Either flashing from USB in DOS might work, or using M-FLASH, I can't say for sure..If not, take it to a PC repair shop or install another/compatibile CPU to flash it up to the latest BIOS..Then you will most likely find joy.

Problem solved now!
 
It was simply an issue of the motherboard needing to be jumpstarted with my first gen ryzen so I could flash the client's x470 motherboard with ryzen 3000 bios.
 
System works with the 8 pin-only CPU power.
 
I'd just never seen this phenomenon of not having 8+4 on PSU until now!  Every system build I've ever done over many years... the PSUs always had 8+4 connectors!

feathers632
Problem solved now!
 
It was simply an issue of the motherboard needing to be jumpstarted with my first gen ryzen so I could flash the client's x470 motherboard with ryzen 3000 bios.
 
System works with the 8 pin-only CPU power.

 

 
As suspected.
 

  bob 16314 was able to identify the BIOS issue

Thanks Cool.
 
@Feathers: You can get a widely available 4-pin Peripheral to P4 Adapter for less than 10 bones if you want/need that to provide extra power for extreme overclocking and have a free connector hanging around..There's also SATA Power to P4 adapters too, but not so widely available as the above adapter.