Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/d2b8a68644a6eaf54fed8a65f89d3100.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563