Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/d7a49f3e1a51048394b8cd2cf211f8ff.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563