Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/63b5d337f3dfa42e14fc4d1f5e89ca5b.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563