joomla - resolve pending 404 error /malware cleanup

please note below msg from godaddy: (there is some malware and issues with 404 pages that need to be resolved ASAP) The remote scanner is detecting an issue with the 404 error page. We expect a random URL would result in a 404, but instead we are receiving a 500 error. For example: $ curl -IL [login to view URL] HTTP/2 500 <<-- server: nginx date: Mon, 17 Jan 2022 20:47:41 GMT $ curl -IL [login to view URL] HTTP/2 500 <<-- server: nginx date: Mon, 17 Jan 2022 20:48:07 GMT The scanner notifies you of this error because it can possibly be related to malware, you can learn more here: [login to view URL] The site is successfully being scanned, but the site error will continue to show until the 404 pages display properly. You may want to contact your developer in order to determine how to fix the 404 error issues.