Thinkpad USB3.0 dock

[PhilipA]

I have a Lenovo X1 and Thinkpad USB3.0 dock. The external monitor has stopped working, with an error message "check connections". I have checked all connections - replaced the dock to monitor video cable but Windows does not detect an external monitor.
I had this error a month ago, but after a trip away with my laptop, I came home, reconnected and all was well. No such luck this time.
The USB is working fine, as it is also my internet connection.
any ideas?
thanks in advance
Philip

[Wim]

Sounds like it could be hardware related. Might be silly, but are the cables good and fully pushed into the video connectors? Do you see any display reconfiguration if you unplug/replug the monitor to the dock? If not, then it sounds like the dock is not detecting a monitor connected and it is a hardware problem.

Wim