Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/f4be6a5fd70d008be72d13fa77b5abda.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563