I’m not sure what you exactly mean by refusing to load a round, but were you able to load a round after it came back from S&W? If not, as a WAG, if you cleaned it after you last shot it 10 years ago could it be that you didn’t quite assembly it correctly? Maybe check YouTube for a refresher and on post cleaning assembly. I know that i shoot my M&P 22 pistol infrequently and like to refer to the instructions for disassembly.