Any software support with the dock?
Win 7 can have difficulty with with more modern USB controllers. Can be a right PITA if you are trying to install Win 7 over USB, however usually a bit easier to solve if its already running like in this case.
Finding the right driver might be the problem. Is it a USB docking station, or a dedicated OEM one designed for that particular laptop using a special dock connector?
If the former, it might be worth plugging it into a Win 10 system to see if that recognises it, and then that may in turn give you a clue as to what driver it needs.
(if it works under Win 10, then upgrading the laptop to win 10 might be another fix (you can still do it free of charge)).