If you have a V3 hub and it’s been updated to support thread in the firmware update which is rolling out now, see the following for one possible cause:
Some background: I have a v3 hub with a mix of Z-Wave and ZigBee devices. The ZigBee are mostly Sengled and OSRAM/Sylvania bulbs, and a generic motion sensor as well. My hub did the recent firmware update that enabled the Thread system. I was reading in another forum a comment about this that said we could check in the app that Thread was present and see info about it on our hubs. In my app, on my hub, I saw no such info even though my hub was showing the correct firmware. So, I rebooted the hub, and then in the app I could see the Thread info as reported. However, from then on my ZigBee devices (the bulbs) started behaving weird. The motion sensor went offline and I could not get it back on. My ZigBee bulbs were randomly turning on and I couldn’t turn them off from the app nor via…
Otherwise, you may need to contact support.