Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/3d55f7c37c2748b01f78363d7dc1c042.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563