I just tested as well and can confirm that this plugin no longer works.
@techAPJ is it possible this plugin of yours is outdated, now that user settings have moved to the user options table? This is not a priority for me right now - perhaps you or @Jared_Needell could update the plugin.
https://meta.discourse.org/t/edit-a-user-setting-for-all-discourse-users/25162/7?u=tobiaseigen