Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/c6a07261114d4eb4a12c3aa2e06e1c56.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563