WD19TBS plugged in but not charging Precision 5530

My docking station is connected to laptop everything else working fine, but the dock station is not charging the laptop, it shows plugged in but is not charging and system is using battery power. What could be the issue? it was charging before before I removed the battery for system cleaning, and after that it stopped charging. I remember that before it used to give me low power warnings too regarding the connection (low power source while booting the laptop). So, what could be the issue here? ps it charges with laptop own charger.