Can your Double Plug be turned on/off manually but you're unable to control it via Home Assistant? Here's what to try if your device goes offline or is unresponsive to Z-Wave commands:

Your Double Plug is a Z-Wave Plus device that has range of 100 feet (line of sight). Even so, interferences like large furniture, thick walls, and metal elements can shorten range. Ultimately range is determined by the specific structure of your home and the strength of your mesh network. If you're seeing connectivity issues, we first recommend healing your Home Assistant network. This function refresh the connections between your hub and devices so that the hub can find the most efficient route to each device.

1. Click on the Z-Wave Control Panel in Home Assistant
2. Under Z-Wave Network Management, click Heal Network

If healing the network didn't help get the device back get back online, here are some other things that may help:

1. Try excluding and re-including the Double Plug directly from the installation location. Similar to the idea behind healing the network, it's possible that the hub hasn't found the most efficient communication route to the device; exclusion can help revitalize these connections. 
2. Try moving the Double Plug to a location closer to the hub, making sure to exclude and re-include it from the new spot. If it connects successfully, the previous spot may have been out of range. 
3. If you have a Z-Wave signal repeater available, try including it in a spot halfway between the Double Plug and hub. A signal repeater is any Z-Wave device that doesn't rely on battery power - switches, relays, smart plugs, or dedicated repeaters. If the issue is caused by interference or range, a signal repeater can help strengthen and stabilize connectivity. After adding the repeater, it's a good idea to heal your network once more. 

If none of the above solves the problem, please let us know! We're always here to help.