Just to throw out some random ideas to try:
It could be your dock is broken from new however thinking up and trying out different tests could be helpful.
What other functions on the dock actually seem to work?
What O/S and version is on the PBP?
What does the message log say? Does it mention the monitor?
If the message log shows the monitor is connected then have you tried manual commands to enable video to the monitor?
- Turn the cable between dock and PBP 180 degrees
- Try a different HDMI cable
- Try a different laptop?
It could be your dock is broken from new however thinking up and trying out different tests could be helpful.
What other functions on the dock actually seem to work?
What O/S and version is on the PBP?
What does the message log say? Does it mention the monitor?
If the message log shows the monitor is connected then have you tried manual commands to enable video to the monitor?