The Parchment template for Inform 7 has not been updated with sound support yet, sorry. It has supported graphics for a long time, but Inform 7 didn’t output a Blorb meaning it couldn’t really be used.
I used the blorbtool.py mentioned in: Inform 7 Released .html not displaying images in web browser - Authoring / Inform 7 - The Interactive Fiction Community Forum and it added enabled the graphics in my HTML release from Inform 7.
But since your sitegen did support sound (although oddly not a sound/music on the opening of the game) I began using it instead.
The Sitegen site shouldn’t be showing an error like that! I’ll investigate. How big is your storyfile?
A bit over 1.5meg. 
Tried a smaller 600k file and still getting the 500 Internal Server Error. 
Is there any way to use it offline?