Not able to login to SNY with Optimum credentials. A "no login form found" error occurs. I believe this might be unique to Optimum subscribers. I trial subscribed for Fubo & AT&T Now and had no problems signing into SNY. But that was a few months ago.
Using the stream.nbcsports.com/rsn/sny in Chrome incognito, I am able to sign in using Optimum credentials.
I am using a TiVo Stream 4k stick right now for this so I might not be able to provide diagnostics.