Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/000c3b86a4e6295a23bd1c3d86de0a8c.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563