The blender blades inside the container are not turning?

If this happens heck the following:

• make sure jug is in place on the unit correctly;
• If the blade assembly had red tabs ( units BL704/BL705 ) make sure the red tabs are pushed out to lock it in place. Also check the base is tight in the glass; 
• always make sure the lid is secure and in place especially if the unit has the interlock system. ( DBL650 );
• also check the jug is in place if it has the interlock system ( DBL650)