Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/0cbf3f8d935f77f81f7ad96650a16a88.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563