First PC build, it worked, and now it does suddenly not

Jul 9, 2018
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Hi guys.

I bought parts for my pc and I assembled it with a friend of mine. We booted it up downstairs when everything was in the pc, but without a monitor, just to test. The pc turned on, every rgb worked, the RAM lit up, GPU lit up, CPU cooler lit ip, all the fans were spinning so we were all good. Then we got it upstairs and tried again with the monitor and we got a display and it said we needed to insert a boot device so that was good aswell. Then we got downstairs to download Windows 10 onto an usb stick, and we got upstairs, clicked the usb in, turned the pc on and after 3 seconds it shut down, and it repeated that. We removed the backplate and we turned it on again and the pc kept on, all the rgb worked, fans spinning etc and it didnt shut down. But we didn't get a display anymore. I didnt have the time yet to troubleshoot, but do you know what the problem could be? It worked and then a boot loop and then no display, but we didn't change anything.. I really am clueless since it clearly worked.

I hope you can help me!