Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/d8b6d447d5fc7a440c71421f9fb0855c.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563