If standard pairing process for remote does not work, it could be the software on the remote itself is out of date. To fix, put remote in pairing mode by holding play/pause button for 5 seconds. Then, instead of adding a remote, use the Alexa app to pair a standard Bluetooth device for the echo you want the remote paired to. You should see an option to connect a device with “remote" in its name. As soon as you select that device your echo will likely tell you the remote needs a software update and it will start that process for you. When it completes, the remote should automatically be paired with the echo.