Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/cc4e38878a1415cc4b8f97fbf2a3dde4.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563