Thanks for reaching out to us, I am sorry this is not working as expected and I am happy to help!
Our first step is to get some additional details about the computer and docking station to help determine what is preventing the second display from being detected. Please let me know the specific model of the Dell Docking station, as well as the manufacturer name and model number of the computer.
Additionally, is the USB Type-C to VGA graphics adapter connected directly to the computer or to the docking station’s USB-C output port? Likewise is the HDMI cable connected to a HDMI port on the docking station?
Thank you for these additional details, they will help to determine our next steps.