2 in 1 laptop touchscreen pen (Dell Active Pen PN350M) doesn't work with photoshop?

I purchased my Dell Inspiron 5491 2 in 1 with a Dell Active Pen PN350M last year. I used this pen in photoshop to draw a few images 9 months ago or so. Since then, I've dusted off my Wacom tablet and have been using that to draw instead.

I just tried to use my Dell Active Pen to draw in Photoshop 2021 and now it's not working? The pen draws in other applications, but when I use the brush/eraser tool (etc) in photoshop nothing happens.

I've seen in other threads that photoshop only recognises drawing on touchscreen laptops as "gestures" and not "fingerpainting", but these threads were mainly written before I was able to use it last year?

I may have accidentally changed a setting when setting up my Wacom tablet (I had issues with pen pressure which I resolved with this method).