I think the tutorial on getting the WebcamStreamer plugin to work needs updating since Twitch apparently changed something earlier this year. I can't get it to work at all; I keep getting a "Whoops! This embed is misconfigured" error. I can stream locally and within my network so there has to be a configuration I'm missing.
Please don't tell me you have your OctoPrint installation available to the whole world via a port forward. This is a very bad idea and is discouraged at all times.
Please take some time to read this post, and consider your options carefully:
Blindly port forwarding OctoPrint is not supported or recommended by anyone on this forum.