Cross check your settings: Configuration -> setting -> capabilities. Lighting should be enabled there. If its still not in the UI, then likely something is wrong,
ssh into pi, check reef-pi log in one tab and restart reef-pi service. It should say why its not enabling the lighting module
Code:
sudo systemctl -fu reef-pi.service # in one tab, to see the logs
sudo systemctl restart reef-pi.service # to trigger restart of the reef-pi service.
The initial log statement soon after the restart is important, they should enumerate all the modules reef-pi is enabling/disabling