Question Pc wont boot, but case fan spin

Oct 22, 2020
System specs:

Ryzen 5 2600
Asrock B450 Steel Legend,
RX 5500XT,
16 GB Corsair Veng Pro,
4 x Deepcool RF120 Fans
Corsair CX550M
1 x M.2 NVMe
3 x HDD

Last night my pc was working fine, but now im trying to turn it on it wont boot, the ram rgb turn on and case fan rgb turn on, but only 2 of them spinning, the cpu and gpu fan didnt spin, Is it PSU or Mobo problem ? Also i need to tell you that i have just upgraded my mobo and procie 2 weeks ago and also the psu is just got back from RMA 1 month ago (Unit replace).

Sometimes it boot but only 3 case fan spin + cpu and gpu, and sometime didnt boot at all but the cases fan spin (again, only 3 of them).