Hello Maarten,
Thank you for posting in Microsoft Community.
I appreciate you raising this concern to us, and I understand that you're having issues with your Surface, projecting displays.
It seems you’re encountering an issue with your Asus ZenScreen MB166C portable monitor not displaying video signal when connected to your Microsoft Surface Laptop 4 via USB-C. Let’s troubleshoot this together:
- Restart your Surface. Press and hold the power button for 20 seconds and release once Windows Logo appears on screen.
- try flipping the USB-C connector over and plugging it back into your Surface. Go to Settings > Windows Update > Check for Updates > Install > Restart.
- make sure that the USB-C connector on the adapter is securely plugged into the USB-C port on your Surface Laptop 4.
- Try disconnecting the cables/adapter and reconnecting it. Restart device as well.
- Try flipping the USB-C connector over and plugging it back into your Surface.
- Try running Surface Diagnostic Toolkit.
- Download Drivers and Firmware: Download Surface Laptop 4 with AMD Processor Drivers and Firmware. from Official Microsoft Download Center
You may also check this link for more: Set up a Surface USB-C to display adapter - Microsoft Support
Please let me know how it goes and hopefully it helps.
Best regards,
Rolando S.