Pen not working

The error message I am getting is No Wacom device connected to your computer. I have the Pen Display Wacom Cintiq Pro 16" connected via HDMI to my computer. The screen is working, but the pen is not. I uninstalled, restarted, re-installed, restarted on many different driver versions with no luck (versions 6.4.3 2021 and non-2021 versions, and version 6.4.2). I followed the instructions here: https://support.wacom.com/hc/en-us/articles/1500006264601-How-do-I-uninstall-and-re-install-the-Wacom-driver-on-Windows-for-a-Pen-Tablet-Pen-Display-or-Pen-Computer-

The pen is still not working. Help!