My Torrents Don't Work - Wat Do? (AKA: How to Get Your Torrents Working Again)

Torrent files each have a web address programmed into them that tells them where the tracker lives and who you are, usually called the announce URL or the torrent URL. If you downloaded a torrent file before we came back up (late March, 2019), your client is looking for love in all the wrong places by trying to contact the old address. To get things working again, you can either download the torrent files again -- they'll automatically be updated with the new address -- or you can edit the 'Announce URL' in your torrent client's settings. Transmission users can do "transmission-edit -r oldurl newurl <directory>", and utorrent allows mass-editing of torrent properties by selecting multiples and then going to properties. Please note that your passkey is unique to your user and remains the same; don't share it if you end up asking for help!

The new announce URL is: https://retrowithin.com/announce.php?passkey=<yourkey>

TL;DR: Re-download the torrent file and reload it into your client, OR edit the tracker/announce url from:
https://retrowith.in/announce.php?passkey=<somegibberish> to announce.php?passkey=<somegibberish>.