Validation HTML5 Question

Dear Sir:

Before the Validator website was updated, I tested my HTML5 page (in attachment) and it showed no errors.  However,when I tested my html5 page after your website was updated, I received this message:
Info: The Content-Type was application/octet-stream. Using the XML parser (not resolving external entities). 
Fatal Error: Empty document, with no root element. ____________________________________
What I did was:I selected file upload, Character Encoding: utf-8,  Document Type: HTML5
I do not know why I am receiving this error, and I do not know what it means.  I researched this answer, but I could not find anything.  I posted my question in stack flow, but it did not work.
Also I clicked on Clean up Markup with HTML-Tidy, but it does not show this feature anymore.
If you could let me know what the error means and bring back the tidy feature I would greatly appreciate it
Sincerely,
Rebecca