Dell Latitude 3510 Power Up Issue

Hi

We have a Dell Latitude 3510, i5, 10th Gen that does not power up.

Screen is fine as on power up pressing D, flickers through the colours.

Dell logo never appears and a disconnect of the battery plus CMOS battery and holding power down to clear discharge does not resolve the issue.  The keyboard lights up and you can hear the fan but nothing appears on the screen.  Nothing appears if another monitor is also connected.  Pressing F2 does not go into Bios or diagnostics.

Warranty expired in November.  Any ideas on what the issue could be?

Help appreciated.