There is a thread on xda for discussion on the bootloader unlock service being down (Error code 24803).
This comment specifically states that Asus has made some progress.
At first while the server was down the http request to the Asus servers for unlocking returned 404. Now they are returning 401 unauthorized (You can see the exact JSON response on the forum post)
It's a little bit of progress so I guess there some still some hope.