When setting up the floodlight, the primary camera is used to control the floodlight as it is attached as an accessory. The secondary camera only uses the power from the floodlight so that you can mount it for better coverage. Since the floodlight is not an accessory on the secondary camera, there is currently no way to directly trigger the floodlight from the second camera.
To provide the flexibility and allow the floodlight to be triggered, Wyze has enhanced the rules engine to allow the floodlight to be triggered by any of your devices. This can only be done by setting up a rule.
Here is a Tip and Trick on how to set up a rule to turn on the floodlight for 15 minutes when another camera senses a person: