Today I decided to upgrade my Home Assistant software to version 0.55. After the upgrade my Philips Hue lights was no long automatically discovered by Home Assistant. A quick fix is to manually add Hue as a light platform to configuration.yaml file. Add below and you should be good to go.
light: - platform: hue host: DEVICE_IP_ADDRESS
I have not looked much into why it is not auto discovered. That must be another time.