A video of this issue would help a ton if possible. When your bike won't start, always check the 3 basic needs of an engine to run. 1- Air 2- Fuel 3- spark. Take out the spark plug and turn the back wheel with the clutch engaged and look for spark. If you see that then you know its good. Next check and see if there is enough airflow and fuel getting to the carb. Is the gas valve set to open? Have you left the coke on? Is your air filter clogged? From what i can discern from your description it sounds like your clutch isnt engaging properly. Perhaps maybe you wore the pads down when the engine seized? Try a clutch adjustment.
Best of luck
Clutch adjustment Guide: