Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/d3e6e71827870fb6b6738ba29e2e8724.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563