Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/bb10a36c532e48f4a5ce73a9d9ac9d39.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563