Xibo client can not get file from server

getFileReturn = xmds.GetFile(ApplicationSettings.Default.ServerKey, _hardwareKey, file.Path, file.FileType, file.ChunkOffset, file.ChunkSize,ApplicationSettings.Default.Version);

getfilereturn = 0 It is caused by?

public byte[] GetFile(string serverKey, string hardwareKey, string filepath, string fileType, double chunkOffset, double chuckSize , string version) {
object[] results = this.Invoke(“GetFile”, new object[] {
serverKey,
hardwareKey,
filepath,
fileType,
chunkOffset,
chuckSize,
version});
return ((byte[])(results[0]));
}