Does not start after replacing the transmission

Remove the starter and see if the engine will turn by hand, also pull the spark plugs so that you are not turning with compression. Are you sure that the torque converter was fully housed when installing the transmission? Post back with your findings.

Turning the wheels will not tell me anything, we need to know if the engine and transmission are locked up.

If the torque converter was left bolted to the drive plate and the transmission was bolted up, the problem will be with the pump drive in the transmission, the torque converter must be fitted to the transmission first and turned and gently pushed in until the splines engage and the pump drive lines up. There will be a good chance that the pressure on the misaligned transmission pump will have damaged the pump. You will have to remove the transmission remove the torque converter and have the pump inspected by a transmission specialist. Torque converters cannot be treated like a conventional clutch that is bolted to the flywheel and the transmission is fed in and bolted up, as the torque converter has two sets of splines and the pump drive to align, it must be done off the car.