Thank you. Frequency does not seem to be the issue. Just cut power to the devices and when powering back on, they began flashing in pairing mode. When I attempted to add them, Hubitat recognized them and many reconnected (although of my 31 front porch zigbee lights, only half seem to be reconnecting). For the devices that re-connected, they seem to be operating as they should.
What could have caused this and anything that I can do to prevent it?
A weak mesh is the most likely suspect here. What kind of zigbee devices do you have? Are any devices reliably/consistently working, or are all ZB devices affected?
I believe you are correct. After going through my home, I observed some of my repeaters were unplugged. I not only plugged them in, but also added in more zigbee switches which should strengthen the mesh. I am working on it still, but I think it is on the mend.