Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/b74af08a9e88665f9bf4ca5a4fbb0068.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563