Question HDMI-1 No Signal problem

Dec 7, 2019
So I got a pre-built a gaming pc from best buy, ik I should have built a pc myself but I didn’t want to risk it since i knew nothing about a gaming pc, anyways The system worked fine but I took out the power cable to the monitor and the power cable to the pc too, I quickly realized that I could just turn off the pc and monitor itself so I plugged it back in and tested if it still worked, but this time it said HDMI-1 no signal. I tried everything to make it work like plugging the power cable in and out and googling how to do it and also reading the manual and checking everything wsd plugged in right but it would still not work. Here is the model computer and monitor I got.
GMA4000BST(pc) and VG245H(monitor).

I also found a rectangular prism under the graphics card with 3 lines on 2 of its sides and a hole under it.