ZGP (Zigbee Green Power) devices are not yet supported in the ZHA integration, however, it now sounds like a developer might be working on code for zigpy, check out the related feature request discussion here → ZHA integration support for ZGP (Zigbee Green Power) devices via zigpy?
https://www.home-assistant.io/integrations/zha#limitations
“ZHA does currently not support devices that can only use the ZGP (“Zigbee Green Power”) profile which is used in a few batteryless self-powered or energy harvesting devices, (such as for example; Philips Hue Click, Philips Hue Tap, and some “Friends of Hue” partnership switches).”
This limitation of no ZGP support in the underlying software library that ZHA depends on is mentioned in the ZHA integration documentation but it is difficult to spot and understand what that means: