Pen connected but will not work

Hi, just bought an Inspiron 7506 2in1 and Premium Active Pen PN579X which I was assured is compatible by the Dell chap on the helpline when I bought it.  I can successful pair the device and it connects but I just can't get it recognised on any app or the desktop.  I've spent hours now on different help sites trying to fix and no luck.  Have tried unpairing and repairing, have tried troubleshooting on bluetooth (says there is nothing wrong).  Please can someone help, this is so frustrating and disappointing after spending so much money and it doesn't work