It is very likely that InterActual Player does not support the disc you have inserted because it's either incompatible with the player or the player is lacking necessary codecs to recognize and play the files on the disc.
However, InterActual Player is created to read only certain DVD discs that are encoded in a special way. This could be the main cause that it cannot play the disc. You should contact the developer of the application in case you run into more problems.
