Recently I also seem to have this problem. Athom’s Philips Hue app version is v5.5.0 and Homey is at v7.2.0.
Interestingly the hue bulbs turn on in the flows where they need to do so. But they don’t turn off anymore via flows.
While manually trying to toggle the bulbs via the Homey app, I indeed get an error saying
Missing Capability Listener: onoff
Furthermore, if I toggle lights via the Hue android application, the state of the lights is correctly reflected in the Homey app…
Anyone else experiencing this issue lately?