10-10-2015 05:00 AM - last edited on 10-10-2015 07:52 AM by Majestic
10-10-2015 12:08 PM - edited 10-10-2015 12:13 PM
Looking at the models that support pen at the PSREF link you included, please notice that it specifies "Active Pen". This is not the same as the ThinkPad Digitizer Pen. That's why it won't work for you.
You need the newer, AAAA battery-powered Active Pen. Apologies, but I don't have a link for it.
Edit to add: Have a look at this - https://support.lenovo.com/us/en/documents/acc100178
Please see the Compatibility section for important info.