Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/9fc6cb0fe53f2b1440b5a40177593f8a.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563