Computer refusing to output to display

[MrChemistryCow9]

My computer got back from a repair shop and said they should replace the motherboard. I replaced it myself to save a lot of money. My 3800x, X570 Taichi, Corsair 16gb Vengeance RGB Pro 3000mhz, Thermaltake Smart M 750W and a 2080 evga. The motherboard LEDS would turn on with everything but no fans would turn on. I pulled out the cpu, mobo, gpu cables and sata stuff and teplugged it in besides at the psu which i was trying to reach. i took out the front of the psu shroud and the repair shop somehow shoved cables in a tiny area that blocked it from pulling all the way off. I screwed around with that for a bit and put it back on. i left the cpu eps cable unplugged but when i tried to power it on it stayed on somehow but no output. the gpu fans were maxed out though. I tried turning it off and plugging in cpu eps power but it would flash on then off. i tried clear cmos as the code 00 said to reseat cpu which i already did and cleared cmos and they changed nothing. the psu should have enough power of 70 watts to keep it powered and it checked the voltages fine along with the grounds. i do not know what could be happening and this is really weird. someone please help me. the x570 also requires an 8 pin and 4 pin eps but it should go fine with a 8pin only. 

[Jimkirk363]

Could be anything, unless u have a supply of replacement parts to try i would suggest u take it into a shop for testing.

[MrChemistryCow9]

2 minutes ago, jimkirk363 said:

Could be anything, unless u have a supply of replacement parts to try i would suggest u take it into a shop for testing.

ok