New PC WON'T turn on, MB's CPU red led light only shines for a moment

[Dawliet]

So my gf and i just bought a new pc, we assembled it completely, but it wont startup. Won't turn on, fans won't work, lights won't work either, and obviously its the same for the screen. But we noticed that the motherboard's cpu red led shines just for a moment, a flash even, when we press the power button.After seeing that we took out the cpu and turns out it had its fan's thermal paste all over it, so that means it was the only think that turned on. I know it sounds weird, but thats it. It wont startup, but its starting to make me go crazy

 

[Paul NZ]

Whats the mobo and cpu?

 

[Dawliet]

My mobo is MSI B150 and the CPU is an I5 6500 (also, how do i answer a certain answer? I can only seem to answer myself to send any response on this page)

 

[Jules Lnt]

My mobo is MSI B150 and the CPU is an I5 6500 (also, how do i answer a certain answer? I can only seem to answer myself to send any response on this page)

 

[Jules Lnt]

I have the exact same problem, MSI B150 Mini ITX with an i5 7600, did you manage to get it fixed?