I just purchased a used SP4, with a pen that I believe is from pro 3 (two side buttons with a clip). The eraser button works and will pull up onenote successfully, but the pen will not write. I tried the troubleshooting options from microsoft including the troubleshooting software. I tried a few different batteries as well, but nothing works. Does anyone have any other advice on this? I guess I'm going to have to get either a new pen or a new tip but I'm not sure what my options are, or if there is something else I can do to fix it.