My second display isn't working on my dell laptop.

First, try unplugging the USB-C cable from the dock (Dock is the little box that has the monitors plugged into it and a single cable going to your dell laptop) to your Dell laptop.  Wait a couple of seconds, then plug it back in. That will usually fix the issue.

If that doesn't work, we may have to dig into display settings by right clicking on your desktop and selecting Display Properties and making sure Extended mode is on and your monitors are arranged in the GUI at the top as they are on your desk. If you need more help, please post a ticket on the helpdesk.