Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/a9b6c34a317e9f6e970d4a1cff74431a.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563