Oh, poor baby! Get it out of the sphag. Cut away all the dead stuff, including dead or broken roots. Then if you still have anything that looks like it might be alive, repot in orchid bark in an unglazed clay pot with a hole in the bottom. My guess is, either it's been overwatered or under watered. If overwatered, let it dry out for a few days before resuming watering. If underwatered soak the roots and media before repotting. Good luck.