Control screen content on iPad Pro via Sidecar and Apple Pencil (G1)

Hi, I use a MacBook Air (M1 / Sonoma 14.4.1) as well as an iPad Pro (9.7" / 16.7.7) and an Apple Pencil (Generation 1) as an input device. I have successfully configured the iPad via Sidecar, Universal Control is set up successfully and I can extend the screen without any problems. My Apple Pencil works perfectly on the iPad OS.

If I switch to the Sidecar integration app on the iPad to see the extended screen, my pencil no longer works. I can only control the screen with my Mac mouse and keyboard. I would like to use the Pencil to retouch images in Photoshop. Which setting have I forgotten?