Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/c6e75f12e3ac4d1e36906f25df34c005.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563