To resolve the issue follow the instructions below. All wemo devices have a led that will show the current status of the devices.

Belkin Official Support How To Reset Or Restore My Wemo
Wemo switch not detected. If you are able to take your smartphone or tablet to a remote. The wemo light switch is blinking orange after a firmware update. Uninstall and reinstall the wemo app then repeat the setup process. Wemo device not in the wemo app this article provides you with troubleshooting steps when your mobile device is unable to detect your wemo after setup. For those who use wemo app to control devices i suggest to turn off wi fi on your smartphone. The wemo light switch wi fi light will blink orange rapidly indicating a successful restore.
Wemo dimmer requires the wemo skill. The wemo light switch has become unresponsive to both the app and manual controls. Reset or restore your wemo device to factory default settings. Wiffi indicator is set to green and blinking. Troubleshooting wemo device issues close all apps that are running in the background then re open the app. Note that it may take 30 seconds for devices to appear when switching tabs on your wemo app.
Try rebooting your router and modem. Close and re open the wemo app to refresh. The wemo light switch is starting up connecting or undergoing firmware update. Before you begin make sure you have the latest version of the wemo app installed. You can tell this because switch timers work which shows that its connected to the wifi but the app still shows not detected. The wemo light switch is not detected by the wemo app.
Press the restart button for 1 second and then release it. This can let us know what can be going on with it. When the wi fi indicator light begins to blink green immediately press and hold the reset button for 5 seconds. For setup instructions click here. You can also use alexa and ifttt with no problem. Wemo switch not detected sometimes your switches or devices say not detected in the app even though you know they are connected to the wifi.
Make sure your mobile device is connected to the wi fi. Confirm if your smartphone or tablet has remote access. To know how click here. Though the app is saying not detected wemo is connected to your home wi fi network and it keeps working on a schedule timer etc. Check the light indicator and confirm if the wemo 3 way light switch is connected to the network. In cases where your wemo device is not detected when linking to alexa try the troubleshooting tips below.
So in case our wemo device is not detected or unreachable this will help us to find a solution.