I recently swapped out the motherboard, cpu, and chasis fan in a previously working computer. I have a 500W Rosewill power supply. The new components are: Asus Prime B450M-A motherboard, AMD Ryzen 5 3400G processor, G. Skill F4-3200C16D-16GVKB memory, and a generic case fan. I removed the original case fan, cpu, motherboard, etc. leaving a SATA hard drive and optical drive. Note: the old system was working fine... it was just time for a refurb. I then installed the new motherboard, cpu, cpu cooler, ram, and remade all of the connections. Now when I try to turn it on, the case fan lights up and spins for maybe half a second. The CPU cooler fan never comes on and the whole thing powers down. At this point, the power button on the front is inactive and only after unplugging it for a few seconds does it begin the cycle again. I have taken it all back apart and re-assembled but end up with the same result. Any ideas would be appreciated. Thanks!