Battery is fully charged, and all the accessories come on when the ignition is turned to on.
But when you crank it all you get is ---key turned - CLICK! ---key released - CLACK! nothing else

 

I'm guessing the "click" and the "clack" is the starter engaging then disengaging.
Sounds like a dead or very weak battery.

 

That's probably the best place to start. Make sure the battery is fully charged and that the cables are clean and tight. If it's still clicking then it's either the solenoid or possibly the starter locked up. Start with the simple and work your way up.

 

How are you testing for battery charge? Simple volt meter? You can have a fully charged battery voltage wise but you can have a bad cell or cells that can't carry a load.

When you go to start the car, use a volt/ohm meter to watch the voltage on the battery. It should be 12.75 or higher. Have someone else try to turn the car over. If the voltage drops under 11, you have a bad cell. under 10 you have two bad cells.

If the battery holds at or above 11.5 then start looking at grounds and/or starter or elsewhere.

 

Inside the starter is a solenoid ( not the one on the fender well) that first engage the starter gear against the Bendix spring and mesh with the fly wheel, and then make a contact to run the starter motor. This insures that the gear is engaged to the fly wheel ring gear before the starter motor turns. Pull the starter and apply power to it from a battery. Careful, the starter will try to spin on the floor. so put your foot on it or hold it some other way. If the gear moves out and the starter turns, then when in the engine something is holding the gear from moving all the way enough to engage the contacts. If the gear moves but the starter does not run, the internal contacts are either[pitted or bad. In this case get a new starter. In the first case check the bushing that is in the flywheel housing and the gear This may be causing the starter shaft to deflect stopping the gear befor contact is made.