We've been using the plugin successfully on other sites and this is the first time we've run into the error: "BackUpWordPress has detected a problem. wp-cron.php is returning a 404 Not Found response which could mean cron jobs aren't getting fired properly. BackUpWordPress relies on wp-cron to run scheduled back ups"
The wp-cron file is in the main directory, as it should be. So not sure why a 404 error is being returned. We're also able to manually make a backup without any problems.