No display on my PC.

I used my pc today normally, in the evening i took out my gpu for taking pictures to put it on sale. After that i put it back everything was working normally, i played some games for 2 hours. Then i went to eat dinner so i turned off my pc when i came back 1 hour after it was turning on but no display. And also my rgb programs are not starting i get that by my cpu cooling lights are staying on startup, and normally you have to keep pressing to shut down button to force shutdown but i can shut it down just by a single press, i tested out my monitor by connecting my laptop and it was working. What might be the problem?