Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/1ac4f038b7a3af6e08c3b9f6c7ae18d8.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563