Before proceeding with any troubleshooting, make sure you're using the SmartThings Classic app, and not the new SmartThings app. While it may seem that the newest version is the appropriate one for your set up, SmartThings is still in the process of transitioning to the new app; in the meantime, it still isn't complete and doesn't allow for full functionality and programming of your devices.
We'd recommend disabling the Health Check in your SmartThings app and performing Network Repair. Here is how to disable Health Check:
1. Tap Menu (Android) / More (iOS)
2. Tap Device Health
3. Toggle the Device Health switch to the OFF state
4. Tap Done
And here's how to perform Network Repair:
1.Click on the Menu icon in your SmartThings hub.
2. Tap Hub is Online
3. Tap Z-Wave Utilities
4. Tap Repair Z-Wave Network
5. Tap Start Network Repair
Before sending any commands to your Smart Plug, wait until you see the "Z-Wave Network Repair finished" message - this can take up to 15 minutes. Once repair is completed, try including the Smart Plug back into your network.
If Network Repair doesn't make a difference, try bringing the Smart Plug closer to your SmartThings hub. Plug it into a wall receptacle near the hub, and then exclude it and re-include it. If the plug includes successfully and stays connected, it's possible the previous spot is out of SmartThings' range or there are too many interferences around that location.
We'd also recommend excluding and re-including the Smart Plug from the installation location directly. Similar to the idea behind Network Repair, it's possible that SmartThings hasn't found the most efficient communication route to the Smart Plug. This can occasionally happen when you include a device near the hub and then move it away to be installed.
Finally, check that your Smart Plug is installed in a spot without too many metal elements surrounding it. Metal effectively blocks Z-Wave signals from coming in or going through. If you notice your Smart Plug is surrounded by metal, try moving it to a different location to see if it still shows as Unavailable.
If you've tried all of the above and are still seeing the same issue, please let us know! Our team will be happy to help.