Oh, cinnamon is hard on roots, not the best choice. It is good used on the plant part. It is a good fungicide and is often used when leaves are cut because of infection.

What medium is your plant in? Sphagnum moss? Any idea what kind of orchid?

In any case, it would be a good idea to pull it from the pot and gently remove the media and let it dry out. Do cut off any black nasty roots and you can use a fungicide on it. It can sit out of the pot for a few days (even dry) while you figure out what kind of orchid it is (can you post a picture?) and get the right kind of media for it and probably a proper pot too, depending on what it's potted in. Don't be too hasty with the potting, gather information, and your result should be better.

Welcome to the forum!