If you needed to re-pair the device in DeConz it will became unavailable in homey. Ensure that the same device is connected to DeConz again and that it is reachable before clicking on 'repair'

A device can get marked as 'unreachable' in DeConz which will make it unavailable in Homey too. If you think this is not the case you can force the device to be available again or you can ignore this behaviour of DeConz permanently (can be changed in advanced device settings).