[SOLVED] Problems booting up newly built PC

Mar 24, 2020
I just built my first PC, and it doesn't work. I have an MSI B360 Gaming Plus motherboard, Ripjaws 8gbx2 DDR4, Intel Core i7-6700k, EVGA Nvidia GeForce GTX 1660, and a Corsair RM 550x PSU.
Each time I turn it on, it will stay on for a couple seconds, then power down. Stay on, then power down. The third time it powers itself on, it will stay on. Among the EZ debug LEDs, the CPU LED lights for a brief moment before the DRAM LED stays on for a couple seconds, then it will turn off and the CPU LED will power on, and that's when the whole thing shuts down immediately. Then it reboots, the LEDs do the same thing, and shuts down. On the third time it powers on, the CPU light comes on briefly, the DRAM light stays on for a couple seconds, but after that nothing happens. The case fans, CPU fan, and GPU fans all run, the decorative lights on the motherboard stays on, but there's no display.
Any help is very much appreciated, I really need this thing to work.