Have power but zero start?

[TexasSteve]

I bought this 2001 GMC Sierra 12 days ago & it has started flawlessly until today. My first thought wasa dead battery, like I gad left the interior lights on, but turning the key gets ZERO attempt at starting (no starter crank) all the power accessories act just fine, the gauge shows a full charge and my battery charger has been on the truck for 4 hours now & still no starter action.

Bad ignition switch? I have noticed that if the key was in too far or not far enough, the cylinder wouldn't turn. But turning the key today & NOTHING! My first thought is that the key cylinder is bad & not sending power to the starter.

Any ideas? I'm at a loss. This is my first modern classic & I have no real clue where to even start looking.