Flux Bluetooth smart bulb uses Bluetooth technology, which allows only one phone or tablet to be connected to the bulb at any given time. If you need a different device to connect to the bulb, you need to turn off Bluetooth with the currently paired phone or tablet, restart the bulb and connect to the bulb from a different phone.
If you need to have multiple devices connect and control the bulb at the same time, please check out the Flux WiFi smart bulbs. They provide all the same features of the Bluetooth bulb and more.
The following article explains the differences between the Flux Bluetooth and Flux WiFi smart bulbs
Difference between Flux Bluetooth and Flux WiFi Smart Bulbs