Hi Sophie_d10,
Thank you for raising this concern to us.
For us to better assist you, we’d like you to answer the following questions:
- What is the make and model of the cable you are using to connect your Monitor to your Surface device?
- Are you using Surface Dock to connect your external monitor?
For the meantime, we suggest that you go to Trouble connecting Surface to a second screen for further information.
You can also check on Monitor’s Compatibility.
Hope this helps. Keep us posted of the outcome.
Regards.