PC only runs with cover off?

PC only runs with cover off?

My PC shuts down when the cover is on and I must shut it down manualy from the on/off button,and the on/off button is staying on “green” static even though there is nothing functioning on the pc…. with the cover off it appears fine…..

Bad Power Supply?
Bad Capacitor(s) on Motherboard?
Bad Fan(s)?

I appreciate any input!