Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/4d5a17a1a58fcb83fa9f8ae9511d714b.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563