Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/1e8f57f7e124cd77f4a7e185f5f399b5.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563