So, I was tinkering with the Plex Media Server settings and then suddenly I got this error in Chrome from my desktop.
“Plex didn’t send any data”
Visiting my server from https://plex.tv/web worked – really weird.
So, going back over what changes I had made, I found the culprit.
Under the Plex Settings > Settings > Network menu option, I had modified the IP6 “Secure Connections” from “Preferred” to “Required”. I changed this back to Preferred and that immediately fixed my issue and the web view was working again.