Make sure you have the latest version of the Alexa app. You can check in the appstore of your device by searching for Alexa and looking for an Update option. Then try these steps:
To play audio from an external source with aux out capabilities (like a laptop or mobile phone) through your compatible Echo device, first configure aux settings in the Alexa app:
1. Select the "Devices" icon. 2. Navigate to your device. 3. Select "AUX Audio," and then "Line In."
Next, connect your Echo device to the external audio source with a 3.5mm audio cable. Set the devices about three ft (one m) apart. Turn on your audio source, and then plug the audio cable into your compatible Echo device and external source.
If that doesn't help, we need a few more details about your setup, such as which devices you're trying to connect and what you are trying to accomplish. Please share as many details as you can so we can offer the best next steps.