Reset an IKEA Kajplats lightbulb by power cycling it 6 times and then leaving it on until it blinks, then it’ll be in pairing mode again. Thanks fishymanbits on Reddit!

Step by step:

1. Turn off the bulb for 30s
2. Power cycle 6 times; on until it lights up, off immediately, count “one one thousand”, repeat
3. On the sixth on, leave it on and wait
4. When the bulb blinks it’ll be in pairing mode again