Nevermind, I think I know what happened. When I upgraded recently, the plugin attempted to modify the database tables. However, the WP user didn’t have permission to make schema changes, so that part of the update failed. I’ve added the permissions for the user, but I need to determine what table updates were attempted.
Yep, the plugin (as well as other plugins, and WordPress itself) will attempt to change the DB schema at different versions so it’s probably best to give the WP user permissions to do this.
You can find the exact SQL used in redirection/models/database.php in upgrade_to_24