I have a ryzen 2600 with a. B450 A pro mobo and 2x8 sticks of ran and it’s not posting but it posted a few days ago
https://pcpartpicker.com/list/6z2yw6Full specs?
CPU
GPU
Motherboard
Ram
PSU
Did it show any unusual symptoms before it stopped working? Did you shut it down and it won't turn back on, or did you move it or something in the meantime?