Why does my shoulder hurt after missing my botox injection by two months for writers cramp?

13 years I've gotten forearm injections f writers cramp. worked well & allowed me to keep my job. D iIsurance company delay took almost two months before I got approval. My shoulder began to hurt like it had done once before when I was late. This time though it has not gone away. So the pain has gone on for an additional 3 months since the last injection and am close to my next set of injections. My Neurologist doesn't know why and Allergan won't answer me directly. Where can I get an answer? Thank you