I inherited an SP4 without power supply or pen/stylus. I purchased a replacement power supply and pen. The power supply works great. The pen worked at first, but when I upgraded the SP4 to Win 10 1903 (from 1703) the pen stopped working. The pen is a generic pen, probably from China and when it was working, it seemed to work pretty well. Also, the pen is not Bluetooth. The package is labeled S Pen Active Stylus. I have rebooted the SP4, I have installed and re-installed the drivers from Microsoft. Nothing has worked. I don't see the pen icon in the task bar area, and there is no pen pointer on screen when I move the pen to the display. Can anyone recommend next steps to get to get this pen and Surface working?