replaced transmission and now car will not start, jus clicks once when turn key each time, checked connections, battery, fuses, HELP!!!!!!!!!!!

Hi. I have a 2000 Lincoln LS 3.9 and am slowly but surely rebuilding it lol so I've learned ALOT. If ur car started fine before trans rebuild I would think neutral safety switch if it not cranking over or starter isn't engaging at all. If u have questions you can email me. I myself have replaced, brake pads, rotors, calipers, coil packs, battery, alternator (a real pain), throttle body, valve cover gaskets (nightmare), and upper timing chain tensioner/ secondary that sounds like rod knock n everyone says junk the motor or wants over $1,000.00 to do. I replaced passenger side for about $80 the cost of new tensioner and it was a breeze, all thanks to a guy on YouTube that drew pictures of him repairing a friend's car. I bought my LS with 140k and now has over 190k miles. I Love this car but if I didn't do the work myself it wouldve been gone. But when these cars are running right they're a real nicely balanced car. My email is Gari2569baldi@gmail.com I'd be more than happy to help w any issues if I can. Good Luck Bro!