The Hacking mini-game in LEGO Dimensions has an interactive portion that requires the use of the Toy Pad. You should see your Toy Pad light up with the colors red, green and blue when the mini-game begins. These colors indicate the three different brick-paths that can be spawned in and out of the mini-game to complete it. In-game these paths are represented by a dotted-line color coded to the path.
To open these paths, you will need to place the player character that you are controlling on the physical panel that represents this color. For example, if you are using Benny the Spaceman to Hack a terminal and need to open the blue path, you will need to physically move Benny's Toy Tag to the panel on the Toy Pad that is colored blue. Once done, you should see a pathway appear within the blue dotted-line section that will allow you to pass. If your Toy Tag is already on the panel and the path is not appearing, try lifting them off the panel for a moment then putting them back on.