Computer won't turn on cpu light isn't blinking but power light is blinking monitor is like computer is in sleep mode key board num lock light is on but can't off it

The computer's death is generally the following three cases:
There is no response to the failure of the main board. Most of the main board after the power supply, even if there is no boot, the main board on the indicator light will rise, if not bright, first check whether it is a power connection or the problem of power itself. In particular, the motherboard 24Pin interface and CPU power supply line interface must be firmly inserted.
The main board lights but can not start. One of the situation is the main board light, indicating that the power has output, but still can not start, this need to check more things, but first did not enter the main board to start self inspection, it is possible to open the key and the BIOS problem.
Check the memory before the start and the beep. Normal boot players will hear a "drop", but if the sound of a buzzing or always "dropping..." is usually caused by a bad contact between the memory bar and the main board memory slot. As long as you rub it back and forth with the gold finger part, you can solve the problem. Of course, the memory slot on the motherboard is broken, which is also possible.

The other classic is "Make it smaller." The less parts the better to reduce what parts that are suspect. This method is well known and you can find many priors by Googling "The Dead PC."

Not knowing the generation or laptop/desktop configuriation, as has already been suggested above, the motherboard LED on(desktop)
would suggest that it is getting power yet the power supply may not be providing other needed voltages to start the system. Test the power supply. RAM is ususally a suspect but a beep code is common. Try swapping out or reseating the RAM one chip at a time - memory dance. Laptops may not be so obvious. Any connections you can reseat may help the situation. Remove the battey and plug it in to see if it boots. If it is a desktop - as stated above - take it apart and put it back together. Remove different components and see if that makes a difference. If it is an older PC it may have an overheating issue with solidified/inadequate thermal paste connection on the CPU. A non-working fan can fumble the boot.
If all else fails a defective motherboard is not usually a difficult fix. If you can get a POST that may give you more info.