Your backup files should still be on disk. You might be able to get that restore dialog back by closing TVRename and launching TVRename from the command line: "C:\Program Files\TV Rename\TVRename.exe" /recover. If that doesn't work, you should be able to do it manually. Go to %APPDATA%\TVRename\TVRename\2.1 in the File Explorer address bar. You'll see your settings file plus numbered backups like TVRenameSettings.xml.0, .1, .2, etc. Rename the current TVRenameSettings.xml to something else as a safety copy, then rename the .0 backup to TVRenameSettings.xml and relaunch. If it's still empty, work through .1, .2, and so on. You can check the file sizes to find the most complete one.