Small Engines (Lawn Mowers, etc.): mower blade, blade, pam

Question
My mower blade engages but the blade doesn't turn. It worked before someone sharpened the blade and put back on. Could it be not turning because the blades not put on correctly?

Answer
 Hello Pam:

 It is Possible that the Blade was put on Improperly. Send me the Make and Model Numbers Off of the Mower and the Engine, Please. With these Numbers I can Locate a Breakdown of this Mower and Better Assist you. Thanks.

 Respectfully

 John