Replace cmos battery with a new battery.  Try clear cmos settings by motherboard RTCRST jumper.

tried that, ill try to post a video of it somewhere and link it in a subsequent reply

@redxps630 

this is the video as mentioned above

Watched video. This is a no post situation, monitor is black because no video sent yet it remains electronically connected to pc vga port (at least in ground).  Look at diagnostic led number at pc front which may give you clue.  Also is power button of pc green or amber?

@redxps630 there are no diagnostic LEDs at the front of the pc, and the power button turns white when i first turn it on, the HDD activity light blinks a bit, then turns off and the power light stays white

remove all memory sticks.  power on.  does it beep.  if no beep the mobo is bad.

1 short beep, short pause, 3 short beeps, short pause, 2 short beeps, long pause

sorry too old fashioned to know how to use discord plus on a restricted pc that is not allowed to install app.

@redxps630  EDIT: i put just one stick of ram in, it gave me a 2 short blinks, pause, 3 short blinks, which it says is bad mobo, ram or cpu, so i put the other stick in and now it turns on and turns off straight after, in any memory channel

@redxps630  another video on the way, easier than typing it all

do you have discord by the way?

https://www.dell.com/support/kbdoc/en-us/000124830/dell-optiplex-and-vostro-beep-codes-and-error-messages

1 stick only: 1 short beep, short pause, 3 short beeps, short pause, 2 short beeps, long pause

@redxps630 i do not have another pc with DDR3 memory to be able to test.

@redxps630 could it not just be the ram and/or the cpu? their both fairly cheap, not sure about the mobo?

cpu very unlikely to die especially in optiplex where you can not raise voltage to fry it.

if all 4 ddr3 tested individually can not make pc post, more likely mobo than ddr3.  it helps if you have another working pc to verify memory works.

statistically we see more mobo issue than memory too at this level (we are not talking about ddr4).  if these memory are original Dell oem for 9010, they should be compatible.  

@redxps630 see second video here, makes it easier than typing (video may not be up yet)