Everything was fine on the evening of Sept. 30 as my last torrent downloaded. The next morning, qBittorrent wouldn't respond to magnets, load peers, or download torrents. In the middle of the status bar at the bottom of the page, the familiar green globe had turned red. My hovering cursor revealed the message – Connection Status: Offline.
I found a number of solutions by searching, "qBittorrent Connection Status: Offline". None worked for me, but maybe others will have more luck.
I finally fixed it with custom settings for the IPv4 Firewall in my Xfinity Gateway. It was set previously at Typical Security (Medium) to block Peer-to-peer apps. I chose Custom Security and made selections that mirrored the settings in medium, except for P2P app blocking, and saved the change. After I selected a random port in QBittorrent's Options>Connection, the cursed red dot went away. I tested it with magnets and torrents and everything seems back to normal.