Hi RemcoR,
Thank you for reaching Microsoft Community. We're sorry for the trouble this has caused you.
The issue that you experience with the pen is quiet unusual knowing that this is a brand new device. This is definitely the experience we want you to have. Let me help you on this and isolate what's causing the problem.
I'll be asking few questions to provide accurate solution.
Does your pen work or is it dead and not charging?
If yes. Were you able to pair it with your device? Can you take a screen shot of what does the status of the pen shows?
Is your Slim pen(old one) works using the Surface duo 2 charge cover?
I hope to hear from you soon.
Kind regards,
Lavenia