Pc won't start

[Huzaifa_6]

Hi, so I have this kinda low end motherboard (it's hp's don't know the exact model), the problem is that my old graphics card was not working so I recently bought Rx550 gigabyte 2gb, and it had windows 8 but the card wanted win10 so I upgraded to Windows 10 64bit but the thing is that since that time my pc is not starting, the led on psu is on. I thought my power button is broken so I tried to start manually from the motherboard but it did not, I put back the power button connector in it and it started after pressing it, there was absolutely no problem after it started it kept playing video games and when I tried to turn it on after shutting it down it happened again and this time it took like 3 hours before it started after pressing the button, I don't know what is the problem here please help

 

[Pentium4User]

even though it would be easier if you know the model but what kind of cpu does the pc have so I can have idea of what model it is?