Hi, Swiss Julian!
Thanks for reaching out to Microsoft Community and posting your concerns. We are sorry to learn that your Samsung monitor will not show a display when connected to your Surface Pro 7 via the Surface Dock 2. Thanks for taking the time to let us know about this and allowing us to help you out.
Thanks for noting that the monitor works fine when directly connected to the Surface Pro 7 using the same USB-C cable that came with the monitor. That helps us isolate the issue here. If I may ask, did you try all USB-C ports on the Surface Dock 2 to test which would work? Also, please ensure that either of the 2 ports in the back are the ones you plug in your cable. Kindly try plugging in the cable to either of the 2 USB-C ports located at the back of the monitor as well. See which of them will work with the USB-C display ports as shown below.
We hope this helps you out. Otherwise, don't hesitate to respond to this thread if there’s anything else that needs to be addressed.
Kind regards,
Janette_Z