Open the Alexa app
Tap Devices
Select Echo & Alexa
Choose your Echo device
Tap Device Settings
Scroll down and tap Factory Reset or Deregister
Confirm the reset if prompted
For a manual reset, press and hold the Action button for about 20 seconds until the light ring turns orange, then blue
For Echo devices with a microphone off and volume down button, press and hold the Microphone Off and Volume Down buttons together for about 20 seconds
Wait for the device to restart and enter setup mode
Set up the Echo again in the Alexa app