Sounds like it has some fluid (oil, gas) in the cylinder. Take the plug out again and pull the starter cord hard a few times. Make sure to ground the plug wire on the post provided on the cylinder head when the plug is removed. See if any spray blows out when you pull it. Replace the plug and see if it will turn over when you pull. You may have tilted the mower to the wrong side during storage or transportation. You can only raise the side with the air cleaner. If this is it, it will smoke heavily for a few minutes after starting. Also check the oil and make sure it is not overfilled and doesn't have a strong gasoline odor.
If that's not the problem, the timing may be off because the flywheel has slipped on the crankshaft from hitting an object with the blade while running.
Another possibility is the compression release is stuck and not opening the valve to allow easy cranking.

Did you put the exact same plug in there? Is it possible the new plug is longer?

I can't help but wonder if you have a stuck valve?

IF it's actually "jerking" the starter cord out of your hand it's either-
You aren't pulling fast enough
or
The fly wheel key has sheared. That causes the ignition timing to be off.

thanks to all it was the fly wheel key, (sheared)