Botox in masseter stopped working

For almost two years, I received Botox injections in my masseter to relieve teeth grinding and achieve a more balanced facial appearance. Initially, it worked wonders, and I followed the recommended three-month schedule. Additionally, I received Botox for my crow's feet, brow lift, glabella, etc. However, the masseter treatment suddenly lost its effectiveness. Despite increasing the dosage to 20 units per side, there was no improvement over the following three sessions spanning nine months.