Are you getting voltage to the solenoid when you try and start it?
Are you getting voltage to the starter when you try and start it?
Does it click-click-click?
Does the interior light come on? any lights like the headlights come on?
Does the interior light, if it comes on, go dim when you try to start it?
When you turn the key on to the first position, do you hear any electronics engage under the hood?
How are you checking your grounds and conections, visual or with a voltmeter or ohmeter?