New CPU and Mobo, fans spinning but no signal to monitor

[xFyrus]

I'm curently helping my brother building a pc since i did it a couple of times without any problems.

 

However, as soon as i tried turning on the pc there are no light on the motherboard at all (except for when you plug the psu in the wall socket for a split second) But the fans for the GPU and CPU are spinning and also the gpu logo lights up.

 

Here are the specs: GTX 970, Ryzen 5800x, Corsair CX 600M and a B550 Aorus Pro V2

 

I tried doing the q-flash with the latest bios and after the flash was done it booted but still with the same outcome as before. I have tried it with a different GPU that was laying around aswell but it did not change anything either :(

What i haven't tried yet is booting the pc outside of the case but since the fans start spinning and i could also do the q-flash, could this really be the issue? I have also tried different ram modules and tried all of the different ram slots on the mobo.

 

He only wanted to upgrade the CPU and Mobo atm so thats why the GTX 970 is still in the build lol...

Thanks in advance! c: