Hello guys. HTTP error 500

When I try to run the offline version of app inventor I got this message after I make a login.
The weird thing is that at first time I run the AI2 offline, I logged in successfully without problems, but after I make reload to the page; that problem occurs, or when I turn off the browser and the server, then try to run it another time.
Please guys help me. I really love App Inventor.
And thank you very much, in advance.

This is the community for the official MIT AppInventor (online)

If you are having issues with an offline version (which is not an official version) then please ask on the community for that builder.