In case you are facing error in scheduled transcoding task and you would like to know details of the error, you can use below code snippet. More details here http://www.itorian.com/2016/04/azure-media-services-transcoding.html

Azure media services transcoding JobState.Error handling

static public IAsset EncodeToAdaptiveBitrateMP4s(IAsset asset, AssetCreationOptions options)
{
    // Default preset settings
    //IJob job = _context.Jobs.CreateWithSingleTask(MediaProcessorNames.AzureMediaEncoder,
    //        MediaEncoderTaskPresetStrings.H264AdaptiveBitrateMP4Set720p,
    //        asset,
    //        "Test-Video-" + 100 + "-" + Guid.NewGuid().ToString() + "-Adaptive-Bitrate-MP4",
    //        AssetCreationOptions.None);

    // Custom preset settings
    string configuration = File.ReadAllText(Path.Combine(_presetFiles, @"H264MultipleBitrateCustom720p.xml"));
    IJob job = _context.Jobs.CreateWithSingleTask(MediaProcessorNames.AzureMediaEncoder,
            configuration,
            asset,
            "Test-Video-" + 100 + "-" + Guid.NewGuid().ToString() + "-Adaptive-Bitrate-MP4",
            AssetCreationOptions.None);

    Console.WriteLine("Submitting transcoding job...");

    job.Submit();
    job = job.StartExecutionProgressTask(
        j =>
        {
            Console.WriteLine("Job state: {0}", j.State);

            // Error handling
            if(j.State == JobState.Error)
            {
                foreach (var task in job.Tasks)
                {
                    if (task.ErrorDetails != null)
                    {
                        foreach (var errordetail in task.ErrorDetails)
                        {
                            Console.WriteLine("Error Message:" + errordetail.Message);
                            Console.WriteLine("Error Code:" + errordetail.Code);
                        }
                    }
                }
            }

            Console.WriteLine("Job progress: {0:0.##}%", j.GetOverallProgress());
        },
        CancellationToken.None).Result;

    Console.WriteLine("Transcoding job end.");
    IAsset outputAsset = job.OutputMediaAssets[0];
    return outputAsset;
}

Here is the error I was getting on Azure portal:

Here is the error details in output after using above code snippet: