If you are still having significant pain, then a low grade infection with an acne producing germ p.acnes might be the cause. Blood work is normal and imaging so so. Read article and take to your surgeon:
Horneff III, John G., et al. "Propionibacterium acnes infection in shoulder arthroscopy patients with postoperative pain." Journal of shoulder and elbow surgery 24.6 (2015): 838-843
Propionibacterium acnes infection in shoulder arthroscopy patients with postoperative pain - ScienceDirect