Is monitor on?If its not unplug your monitor from power then re-plug your monitor to gpu and then plug monitor back in power.
The second clear cmos, unplug your pc from wall (keep switch to I), remove shiny battery, hold power for 30s~ then plug back battery,plug back in power (keep switch to 0, then switch back to I) and try to power it up.
Worst case scenario your PSU has died.
Can you post specs of your PC?(ill suggest you one more method if you give me specification of your PC)
CPU-
GPU-
RAM-
MOtherboard-
PSU-