Computer Won't Turn On After Sleep Mode?

I have a huge problem. This morning, when i turned on my computer, everything was fine. The computer booted up as usual. Then later, when i had to shut it down, i accidentally pressed the sleep mode button. PC did enter sleep mode but after that I tried to turn the computer on again and it just won't turn on.
The monitor is all black and the computer is not responding.

Unplug the power cable, wait 3-4 seconds and plug the power cable back in.

Turn on your pc and try again to see what happens.

I suggest you check for connection problems, monitor cables disconnected etc. I know you will say it worked fine before you set it to sleep, but believe me, you never know. If the problem persists, you must consider clearing the BIOS from the motherboard jumper or changing a PSU, in my technical experience.

Standby, or sleep mode as it is sometimes called, has always been problematic. It is not uncommon at all for people to experience sleep mode problems.
Sleep mode has had a lot of trouble with waking up from its idle state due to the nature of what the computer has evolved into today. Many times, decides plugged into the USB Drives (iPod’s, USB Hubs.etc) can cause this issue as they are not receiving enough power and suck more of the system resources during sleep mode. I recommend disabling this on desktop computers for this reason that trying to reboot your computer after it fails to restore from sleep mode does not always guarantee/protect your data; thus I turn off the ability for my computer to set itself into that state.