When you are recording your video with one or multiple markers (whether on a Swivl CX, C Series, or a Gen 2 robot), always check to make sure that all the markers are paired to the base. A fully paired primary marker will have two solid green LEDs, and a paired secondary marker will have a single solid green LED.
Check the Home screen. When markers are turned on (and paired), they'll appear lit up in your marker menu on the screen(1). You can tap on the icon to adjust markers' settings: color, sensitivity, or select the primary one(2).