Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/8f8e67c8a8d521b041ea4114ea4ef03c.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563