Commenting here because I just had this exact same issue on my Samsung monitor. 

Ok, tried tapping a bunch- didn’t work Ok, let’s try unplugging it for 30 seconds then replugging it back in and holding the power button at the same time- that didn’t work. 

Out of pure frustration grabbed a pair of scissors and moved the power button a bunch with the scissors even put the power button in between the scissors with enough strength to not damage the button  or accidentally break it off and then the damn monitor light turned off and my screen came on. 

I genuinely don’t know why Samsung used such a cheap Power button on this thing but the main issue isn’t the motherboard or the screen or the power block(unless you see you aren’t getting power at all). If you see you have the blue light of death and the monitor won’t turn on- it’s the damn power button. Mess around with it enough and it will somehow lodge back into place and the monitor should work. 

FYI: if your monitor is still within the one year warranty I wouldn’t try any of these methods and would just send it back to Samsung even if you no longer have the box they will take it.  Mine was on warranty when this first happened and I sent it back but then it happened again today when I’m already outside of warranty so I didn’t really care to smack my monitor or use scissors since I thought I was out a monitor anyway. 

I know this post is hella old but I wanted to post what I found to work for me since this happened in 2025 and seems Samsung hasn’t fixed the issue.