Login to your server and change the file under your plugin directory
wp-content/plugins/all-push-notification/pushnotification/class-pushnotification.php
change lines 2 and 3 from:
require_once '/class-pushnotification-android.php';
require_once '/class-pushnotification-ios.php';
to:
require_once plugin_dir_path(__FILE__) . 'class-pushnotification-android.php';
require_once plugin_dir_path(__FILE__) . 'class-pushnotification-ios.php';
