Updating PHP from 7.0 to 7.4 breaks Matomo

I’m running the the latest 3.x under Hostgator, and just upgraded PHP from 7.0 to 7.4. Now Matomo won’t let me in. It throws an error, and also downloads a small file, both copied below. I’d imagine it wants me to put this file somewhere, but I have no Idea where. I’d be very grateful for any help that someone can offer. Thanks!
-------error------------

**Fatal error** : Uncaught Error: Class 'Piwik\SettingsServer' not found in /home4/vparunak/public_html/cyber-chapel.org/analytics_p/core/testMinimumPhpVersion.php:87 Stack trace: #0 /home4/vparunak/public_html/cyber-chapel.org/analytics_p/core/testMinimumPhpVersion.php(176): Piwik_ShouldPrintBackTraceWithMessage() #1 /home4/vparunak/public_html/cyber-chapel.org/analytics_p/core/testMinimumPhpVersion.php(195): Piwik_GetErrorMessagePage('<p><strong>Mato...', false, '<ul>\n ...') #2 /home4/vparunak/public_html/cyber-chapel.org/analytics_p/core/bootstrap.php(30): require_once('/home4/vparunak...') #3 /home4/vparunak/public_html/cyber-chapel.org/analytics_p/index.php(21): require_once('/home4/vparunak...') #4 {main} thrown in  **/home4/vparunak/public_html/cyber-chapel.org/analytics_p/core/testMinimumPhpVersion.php**  on line  **87**

-------downloaded file------------

<?php

/**

 * Piwik - free/libre analytics platform

 *

 * @link https://matomo.org

 * @license http://www.gnu.org/licenses/gpl-3.0.html GPL v3 or later

 *

 * @package Piwik

 */

if (!defined('PIWIK_DOCUMENT_ROOT')) {

define('PIWIK_DOCUMENT_ROOT', dirname(__FILE__) == '/' ? '' : dirname(__FILE__));

}

if (file_exists(PIWIK_DOCUMENT_ROOT . '/bootstrap.php')) {

require_once PIWIK_DOCUMENT_ROOT . '/bootstrap.php';

}

if (!defined('PIWIK_INCLUDE_PATH')) {

define('PIWIK_INCLUDE_PATH', PIWIK_DOCUMENT_ROOT);

}

require_once PIWIK_INCLUDE_PATH . '/core/bootstrap.php';

if (!defined('PIWIK_PRINT_ERROR_BACKTRACE')) {

define('PIWIK_PRINT_ERROR_BACKTRACE', false);

}

require_once PIWIK_INCLUDE_PATH . '/core/dispatch.php';

Hi,

Matomo doesn’t want you to put this file anywhere, but rather it is the content of the index.php already.
Are you sure you have set up your web server correctly to execute PHP instead of delivering it to the user?

I don’t really have any explaination for the first error apart from files missing.