Trying to connect with a browser tab which has connected before, I now see " Plex Web would like to sign in to your Plex account. This application is at app.plex.tv and is not hosted by Plex. Continue only if you recognize this server and wish to grant access."
This has never occurred before. Should I be concerned?
Inspect your web browser add-ins and create the necessary exceptions in their settings for the domain plex.tv.
Anything that can filter out parts of web pages, rewrites URLs, or clears cookies and website data from local browser storage.
Refreshing the web app in the browser can’t hurt either (F5).