When I connect my EliteBook to my Dock and Daisy Chain USB-C cable, sometimes there are issues with the screens coming on.

Historically I’ve just tended to restart, but you don’t need to, you can just restart the display manager, as below.

$ sudo systemctl restart display-manager

This will log you out, so it’s almost as inconvenient as a restart, but it tends to fix any issues I’m having.