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We can work through this and determine what is wrong with your engine. The first thing I need to know is if the oil is filled to the appropriate level.
Also please remove the spark plug and see if the engine turns over with the pull rope and no plug installed.
If this happens then I want to remove the recoil assembly and check the flywheel to make sure that the starter gear has not broken and gotten caught between the ignition coil and flywheel. (this happens a lot). If everything checks out then use a large socket that fits over the flywheel bolt and see if you can move the engine in either direction.(still with the plug out) If none of this works then you may be looking at a seized or blown engine