Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/67fc1fbca0a1c2e3b0d5c4f8b4b4c389.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563