I noticed too late that index.html is:
<meta http-equiv="REFRESH" content="0; url=html/index.html">
pointing to other index.html within "html" dir.
I replaced it with:
<a href="html/index.html">Go</a>
within the <body> tag and from 20 minutes Calibre fights with it

Unfortunately it hang on 67% (progress not increases but it seems working cause details are coming).
I'm going to wait a hour.