System not working - 3 flashing lights on motherboard near the BIOS Flashback+

[pandalord]

Hi,

CPU: AMD - Ryzen 5 2600 3.4 GHz 6-Core Processor
MoBo: MSI - B450 GAMING PRO CARBON AC ATX AM4 Motherboard
Memory: Corsair - Vengeance RGB Pro 16 GB (2 x 8 GB) DDR4-3200 Memory
Video Card: EVGA - GeForce GTX 1060 6GB 6 GB SC GAMING Video Card
SSD: Crucial: MX500 500 GB 2.5" Solid State Drive
HD: Seagate Barracuda 2 TB 3.5" 7200RPM Internal Hard Drive
Power Supply: Corsair - TXM Gold 550 W 80+ Gold Certified Semi-Modular ATX Power Supply
Case: NZXT - H500i (white)

So I've spend the best part of this afternoon trying to figure this out but feel like I don't know what to do next.

So as my first go at it I set up the MoBo on the box it came in, connected the CPU, attached the fan, plugged in the RAM and Video card then hooked up the power and monitor.

Turned it on and the only thing that happened was a red light flashed 3 times near the top left of the MoBo (BIOS Flashback+ button I believe). no fans started up and no lights elsewhere.

I then thought to try it in the case with more things connected but got the same result.

I headed onto this and other forums to see what the problem could be and tried the following:
Starting the system with no Videocard (only the 3 x red flashing light)
Starting the system with no RAM (only the 3 x red flashing lights)
Starting the system with only the CPU, CPU Fan, 8-pin and 24 pin connectors hooked up (only the 3 x red flashing lights)

It's my first attempt at building a pc so I'm a little lost on what to do now. Any help would be much appreciated. Thanks!

 

[Calvin7]

You neglected to connect power to CPU_PWR2. This is not optional. Try following drawings in the motherboard manual.

 

[pandalord]

You neglected to connect power to CPU_PWR2. This is not optional. Try following drawings in the motherboard manual.

Hi, Thanks for the feedback, I did try looking into that as an answer but I read some posts that suggested it didn't need it and there isn't a CPU_PWR2 (4-pin) cable as part of the PSU. Not meaning to sounds really silly but is there something I'm missing here? Have I managed to get the wrong PSU? or should I be looking to purchase another cable?

Edit:
So I've been looking over it again today and I'm still a little confused as to what the best way is to connect a 4-pin cable as well from the PSU that I have (Pictures attached)

Is there some way to connect it with the other cables supplied? (Using a something like a Molex Cable Adapter)?

Nervous about doing something that might be wrong or possibly break something.

Thanks

 

[DatZebra]

I have the exact same issue, I was using my PC and it shut off randomly. I did some research and bought a new PSU. I put the new PSU into my system and plugged everything in but I get the red flashing for flashback everytime I unplug and replug in the power supply. I'm not sure what is causing this but I feel you ever got the problem fixed please tell me how.