The most common causes can be fixed yourself in a few minutes. Go through the steps in order.
Docking station or monitor
Check that the docking station has power (power adapter connected, light on).
Unplug the cable between laptop and docking station, wait 10 seconds and plug it back in firmly.
On the monitor, check that it is switched on and the correct input is selected (Input or Source button).
Windows: press Windows key + P and choose Extend. Mac: open System Settings › Displays.
Restart the laptop with the docking station connected.
Install Windows updates. They often include new drivers for docking stations.
Camera
Check whether the camera is covered (shutter on the laptop) or turned off with a key (camera icon on the keyboard).
In Teams, Zoom or the browser, select the correct camera. Teams: Settings › Devices.
Close other programs that might be using the camera.
Windows: open Settings › Privacy & security › Camera and allow access for apps. Mac: open System Settings › Privacy & Security › Camera and allow the program.
Restart the laptop.
Note: If the image flickers, try a different cable or port. If nothing helps, contact support with the models of your laptop and docking station and a photo of the connections.
For sound and microphone, see “Set up sound and microphone – Windows”.