Computer turns on but no display to the monitor and no power to the keyboard and mouse

[blocklandfalcon]

So I recently installed liquid cooling and a new power supply last night and the computer was running just fine that night and today when playing GTA V, when all of a sudden the computer possibly froze. I resorted to shutting down the computer and when turning it back on, it would turn off again, I assumed it was the cpu being too hot to start up, so I reapplied thermal paste with care and after doing so, the cpu, fans, hard drive were working completely fine, but didn't get a display on the monitor and also noticed no power going to the. mouse and keyboard. I was very sure it was the motherboard not working properly, but I want to know what you guys think.

UPDATE: I did some tests by clearing the BIOS via battery, removing battery, replacing battery, and even reseating everything. Nothing has changed. What I did notice is that the light on my motherboard doesn't move over to 'BOOT' like it did before, and as of now it's staying on 'DRAM'. Surely it was never switching to boot ever since this has started happening.

UPDATE 2: Made a mistake and the LED was indicating the CPU

 

[timmy_area51]

have you checked your RAM ?

 

[blocklandfalcon]

Yes, I even tried moving it to a different slot, still nothing

 

[timmy_area51]

if it doesn't power anything then it should shut down by itself after a while ? right ?

 

[blocklandfalcon]

Last time I was testing it, the computer turned off after maybe a minute or two

 

[timmy_area51]

but it should shut down within seconds if its critical

 

[blocklandfalcon]

Well I dont know what's going on with that. Pretty stuck here.