For some power supplies the fan starts only when needed. Not sure if it's the case with the PSU you have.
Can you test a different GPU, or test yours in a different PC? Is there a case speaker connected to the motherboard?
yup psu fans tend to start only when needed.
what build is your psu?did you recently make any hardware changes?
if the processor fan is spinning then either your motherboard is not booting up or the gpu is dead and not sending any video signals
try removing the gpu and starting the pc if the video signal returns its probably the gpu
if it dosnt return then theres a possibility that the bios is not booting.
if your cabinet speaker is connected you will hear a small beep when the bios boots also the lights on your keyboard will stop blinking
so if thats not the case try cleaning your ram sticks and check for bad ram.
reset your cmos
well i think you misinterpreted
remove the gpu connect the monitor to the motherboard's vga port and check for video signal if you get the signal and the pc boots properly its just a faulty gpu
if not try removing the ram and cleaning it with an eraser and REinsert it before you boot again.
try it without the gpu first then if it works try it again with the gpu
reset the cmos check if the bios boots
and do check if the cabinet speaker is connected as most motherboards give signals in somtehing like a morse code to identify the problem the key can be found in your motherboards manual
if you did all this with no luck then id probably once check the system with just the processor and ram on board an then with another psu
this way you can isolate the faulty component
if the problem still persists then most probably the motherboard is dead.