If a Z-Wave device is showing that it is offline, then it is not responding to commands or communicating with the Z-Wave network.
As soon as a response is received from a malfunctioning Z-Wave device, it is automatically put back into online status.
Verify the device has power and is turned on.
Verify the Z-Wave device is within range of the Z-Wave network.
Verify if a successful network rediscovery has been performed recently.
If a Z-Wave device is still offline after attempts at network rediscovery, it may be necessary to delete and relearn the Z-Wave device in order to bring it back online.
Refer to the below guides for proper Z-Wave network setup and panel specific instructions to Add/Remove devices and run a Z-Wave Network Rediscovery.