OptiPlex 9020 no power light but turn on in no display

first try replace cmos battery with a brand new one then clear cmos settings via motherboard jumper.  fan spin does not mean much.  do a Dell psu bist test to verify psu still works.  you have a no power or no post situation.  a bad psu can still turn on fan.

@redxps630​i did everything you said all i know their no power light on the Powe button but when you plug it in the fan start spinning fast then when i try turning it off by the Powe button it don't turn off i have to unplug it i did recently replace the cmose batter because everytime I set the time on the bios it didn't save in it wouldn't go to windows because when windows was booting up it would go to no display in i try reinstalling windows then when i would install the graphic driver it would go to no display as it was installing then when i turn the computer off again in turn it back on it started doing the same thing again when loading windows again

if you get some video then it is not No POST.

confirm you have cleared cmos by motherboard CLR CMOS jumper.

@redxps630​ what i did i move the cmose to the to the pin that reset the bios in it still does the same thing

Try unplug power sw cable and jump start motherboard