My craftsman lt1000 won't turn over. It has new battery. New spark plug. The fuel lines are clean

It could be that a fuse is broken.
Or if the mower has a switch under the seat so when you get off it turns off,it might be that switch is stuck.
If those are good try putting a little fuel in the carb before starting.
Good luck.

So you turn the key and get nothing , right? Or does the engine starter spin the engine but it doesn't fire up, need all the details. This is trcky and must be done in a quiet space. Raise and lift of the hood and have one person put their headright in front of the carb, turn the key to on just short of start, did they hear a single click down by the carb? If not it could be a loose fuel shut off valve under the carb, check the wire.