Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/cf3c8b8b19b13e538b1b29330f3c2a65.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563