Solutions:
The bulb will not be detected on the new device if it has been connected on another device, so we have to restore a factory setting operation on the bulb to allow the bulb to pair successfully and operate on the new device. Switch on the bulb for at least 30 seconds, then switch it off and restore it to the factory settings as follows.
Light up the bulb and when it reaches maximum brightness (usually within 5 seconds), turn it off immediately; repeat the above steps 3 times; light up the bulb and you will see the bulb switch to red / green / blue / white continuously and the operation is complete. Then re-open the mobile app and the smart bulb will be detected.