Open the Alexa app
Tap Devices
Select Echo & Alexa
Choose your Echo device
Tap Device Settings
Tap Factory Reset or Deregister
Confirm the reset
For Echo Dot with a microphone off button, press and hold the Action button for about 20 seconds
Wait for the light ring to turn orange, then blue
Wait for Alexa to announce setup mode
For Echo devices with a Reset button, press and hold the Reset button until the light ring turns orange
Wait for the device to restart and enter setup mode
For Echo Show, swipe down from the top of the screen
Tap Settings
Tap Device Options
Tap Reset to Factory Defaults
Confirm the reset
After resetting, open the Alexa app to set up the device again