Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/9dbfc99e7f01b6c0c8ff65dd7a1804cd.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563