Why wont anything come on monitor screen?

Sam I Am,

Start trubleshoot from monitor

• Connect it to laptop or any other supported video output to check wheter monitor is works fine

if the monitor working,

you should begin to troubleshoot the PC

Here you can find the Video card replacement guide. you can remove the video card and clean the card and motherboard interfaces and reinstall video card and check whether PC video out works fine

if above steps not help to solve you issue or if you PC run with on board graphic controller you can remove RAMs and clean the interfaces and reinstall RAMs properlly. and check whether vedio out start to work back

Here you can find RAM replacement guide,

Cheers!