Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/ee1a158bfce5c24a79a6a4a76c4ce75a.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563