The custom autoload file is not needed any more (autoloading via composer).

autoload.php

@@ -1,43 +0,0 @@
-<?php 
-
-/* ----------------------------------------------------------------------------
- * Easy!Appointments - Open Source Web Scheduler
- *
- * @package     EasyAppointments
- * @author      A.Tselegidis <alextselegidis@gmail.com>
- * @copyright   Copyright (c) 2013 - 2020, Alex Tselegidis
- * @license     http://opensource.org/licenses/GPL-3.0 - GPLv3
- * @link        http://easyappointments.org
- * @since       v1.2.0
- * ---------------------------------------------------------------------------- */
-
-function register($namespace, $path) { 
-    spl_autoload_register(function ($class) use ($namespace, $path) {
-        // project-specific namespace prefix
-        $prefix = 'EA\\' . $namespace . '\\';
-
-        // does the class use the namespace prefix?
-        $len = strlen($prefix);
-        if (strncmp($prefix, $class, $len) !== 0) {
-            // no, move to the next registered autoloader
-            return;
-        }
-
-        // get the relative class name
-        $relative_class = substr($class, $len);
-
-        // replace the namespace prefix with the base directory, replace namespace
-        // separators with directory separators in the relative class name, append
-        // with .php
-        $file = $path . '/' . str_replace('\\', '/', $relative_class) . '.php';
-
-        // if the file exists, require it
-        if (file_exists($file)) {
-            require $file;
-        }
-    });
-}
-
-register('Engine', __DIR__ . '/engine'); 
-register('Themes', __DIR__ . '/themes');
-register('Plugins', __DIR__ . '/plugins');