Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/b24ad9d4e66ce02abca06924c84795a7.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563