question

Looks like the Audio file is too long.

I tested the Audio URL and received the following error in the CloudWatch Logs:

"request": {
        "type": "SessionEndedRequest",
        "requestId": "amzn1.echo-api.request.bd36718a-2e3a-434e-8332-ae4caee0723a",
        "timestamp": "2018-01-02T17:36:17Z",
        "locale": "en-US",
        "reason": "ERROR",
        "error": {
            "type": "INVALID_RESPONSE",
            "message": "Invalid SSML Output Speech for requestId amzn1.echo-api.request.7db5a314-3e90-4f6d-91c4-d64d275c9a0b. Error: The audio exceeds the allowed maximum length of 90000 milliseconds"
        }

Alexa will send back error information to Skills. To see the details, print out the Event JSON by adding:

console.log("===EVENT=== \n" + JSON.stringify(event));

to the exports.handler function:

exports.handler = function(event, context, callback) {
    console.log("===EVENT=== \n" + JSON.stringify(event));
    var alexa = Alexa.handler(event, context);
    alexa.APP_ID = APP_ID;
    alexa.registerHandlers(handlers);
    alexa.execute();
};