Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/bd241d40d1f096e40e6b7f4e8b7a8a74.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563