Never had that issue with an AI light unless the firmware was out of date or the router was blocking it.
In the AI app, select the master AI light, then go to "settings", and make sure the firmware is current. Then do the same thing on the child light. Oh--and make sure bluetooth on your phone/iPad/computer is turned on.
Might also want to check the MAC address for the lights and compare those to the device list connected to your router. Sometimes the router is set to prevent connection for a particular MAC address.
You can also log directly into the light by opening a browser on a windows computer and typing:
64-_____________.local/index.html
Change the "red" number above to your light model (ie: Hydra-32, 52, or 64) , and replace the underlined area in the address to your lights' serial number. Then just check the firmware version and settings in the browser.