This response works fine on the emulator in the dev console and the alexa mobile app... On the echo devices (dot, show, and fire tv), it skips the audio tag. Are those not supported with audio tags? I confirmed the mp3 was 24kHz and 48kbs
"outputSpeech": { "type": "SSML", "ssml": "<speak><audio src=\"https://example.blob.core.windows.net/hello.mp3\"/><p>Would you like to check your account or hear other options?</p></speak>" },