Botox injections to the masseter are tailored to each patient. There are several reasons why your treatment may not have been effective:
"Imposter Botox" - There are several versions of botulinum toxin available. In the United States, two are currently FDA approved, Botox and Dysport. Beware of other versions of Botox which may be counterfeit, watered down, or "Chinese Botox" which has a track record of unreliable results.
Poor technique- Botox must be injected into the proper location of the masseter muscle.
Not enough units- Every patient has a differnent dosage requirement and the treatment must be tailored to your anatomy
Followup treatments- Botox jaw reduction requires a series of treatments with each treatment creating more impact than the previous treatments
Poor Habits- Patients who continue to chew gum, eat chewy foods, etc, will lead to less impressive results after treatment.