Reset Amazon Echo
If Alexa can’t hear you, then try moving the device away from any obstructions. Keep the device at least 8 inches from the wall.
WiFi connection issues
If your device refuses to connect to Alexa WiFi when you are setting the device. Power off all the networking gear, including modem, dot and router.
Reset Echo Dot
If you have tried all of the above steps and your Echo Dot setup is still unresponsive, you will have to take the nuclear solution. You need to perform a factory reset on Dot and send it back to default settings.
Remember that doing a this can delete all skills and performance, so you need to set it from the scratch.
Herev download Alexa app