该问题可能是由于您的AWS凭证不正确或AWS Mediaconvert作业设置错误引起的。您可以尝试以下步骤进行解决：

1. 确保您的AWS凭证正确配置，并且您具有AWS Mediaconvert服务访问权限。
2. 确保您创建AWS Mediaconvert作业时，已正确配置作业设置，如输出流和视频编码设置等。 以下是一个示例代码，可以用于创建AWS Mediaconvert作业：

// Include the SDK using the Composer autoloader require 'vendor/autoload.php';

// Instantiate the client with your AWS credentials use Aws\MediaConvert\MediaConvertClient; $mediaConvert = new MediaConvertClient([ 'version' => '2017-08-29', 'region' => 'us-west-2', 'credentials' => [ 'key' => 'your-aws-access-key-id', 'secret' => 'your-aws-secret-access-key', ] ]);

// Create the job from the input file and output settings $result = $mediaConvert->createJob([ 'Role' => 'arn:aws:iam::111111111111:role/MediaConvert_Default_Role', 'Settings' => [ 'OutputGroups' => [ [ 'Name' => 'File Group', 'Outputs' => [ [ 'ContainerSettings' => [ 'Container' => 'MP4', 'Mp4Settings' => [ 'CslgAtom' => 'INCLUDE', 'FreeSpaceBox' => 'EXCLUDE', 'MoovPlacement' => 'PROGRESSIVE_DOWNLOAD' ], ], 'VideoDescription' => [ 'ScalingBehavior' => 'DEFAULT', 'TimecodeInsertion' => 'DISABLED', 'AntiAlias' => 'ENABLED', 'Sharpness' => 50, 'CodecSettings' => [ 'Codec' => 'H_264', 'H264Settings' => [ 'InterlaceMode' => 'PROGRESSIVE', 'NumberReferenceFrames' => 3, 'Syntax' => 'DEFAULT', 'Softness' => 0, '