Add Shelly push update troubleshooting list (home-assistant#28470)

Co-authored-by: Shay Levy <levyshay1@gmail.com>
Co-authored-by: J. Nick Koston <nick@koston.org>

Author: 3 people

source/_integrations/shelly.markdown

@@ -51,6 +51,17 @@ Generation 1 devices use the `CoIoT` protocol to communicate with the integratio
 
 We recommend using `unicast` for communication. To enable this, enter the local IP address of the Home Assistant server and port `5683` into the **CoIoT peer** field and push **SAVE** button. **This is mandatory for battery operated devices**. After changing the **CoIoT peer**, the Shelly device needs to be manually restarted.
 
+Home Assistant will display a repair issue for the Shelly device if push updates from this device do not reach the Home Assistant server.
+
+The list below will help you diagnose and fix the problem:
+
+- Check if your Shelly devices have a properly configured `CoIoT peer`.
+- If you can't find the `CoIoT peer` settings in the device's web panel, it's probably using an ancient firmware version, and you should update it to the current one.
+- If Shelly devices are in a different subnet than the Home Assistant server, you should ensure communication on `UDP` port `5683` between these subnets.
+- If Home Assistant is running as a virtual machine or service on an operating system other than Home Assistant OS, you should open `UDP` port `5683` on the device's firewall and/or ensure that communication from this port is redirected to the Home Assistant service.
+- The missing push updates may be related to the WiFi network range. If using a WiFi network with several access points, enable **Internet & Security** >> **WiFi Client AP Roaming** option. Consider moving Shelly device closer to the WiFi access point. Consider adding another WiFi access point, which will improve the connection quality with the device.
+- If you think your Shelly devices are working correctly and don't want to change your network/configuration, you can ignore the repair issue. Still, you must know you are giving up the best experience of using first-generation Shelly devices with Home Assistant.
+
 ## Shelly device configuration (generation 2)
 
 Generation 2 devices use the `RPC` protocol to communicate with the integration. Battery powered devices need manual outbound WebSocket configuration, Navigate to the local IP address of your Shelly device, **Settings** >> **Connectivity** >> **Outbound WebSocket** and check the box **Enable Outbound WebSocket**, under server enter the following address: