Rivet Software for streaming mac onto xbox

I had download rivet, and it worked wonderfully. Everytime I opened my xbox I would be able to access music/videos etc.. But after about a week of use my xbox no longers sees it. I have no changed any settings on both my xbox and macbook. I have deleted and reinstalled rivet about a million times and that doesnt seem to help.

Why would my xbox just all of a sudden not see the device?

Thanks