The common risk factors for non union of humerus fracture are open fracture, highly comminuted fracture pattern, significant displacement of the fracture fragments, smoking,
diabetes, NSAID’s, infection and hypothyroidism.
In your case, smoking could have aided in non union of the fracture, but there is a need to rule out other causes as well.
Any surgery the previous one you got done or the revision surgery your doctor has advised requires that you quit smoking for it to heal.