Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/760b1de9e1de48bab6f17ef32e71bb42.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563