Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/15e85b33d7a6574ad4500a292c2f919e.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563