The website Schema.org is down, currently showing a “500 Server Error”. A 500 Server Error could be the result of several different things, such as too much traffic for the server to handle, a Denial of Service Attack, or a misconfiguration on the web server or website itself. So, at this point it’s just speculation as to why Schema.org is down.
In the meantime, here are a few resources for generating Schema.org code for your website:
H/T to Dave Davies for mentioning that Schema.org is down.