The Story Meta Data section of a story HTML file current has two different formats:
(note: the following data formats have been simplified for readability sake.)
1. The older "Twine 1.x" format.
This format can be imported into / read by: Twine 1.x application, TweeGo
<div id="store-area" data-size="876" hidden>
<div tiddler="Passage Name 1" tags="tagA">...</div>
<div tiddler="Passage Name 2" tags="tagB">...</div>
2. The newer "Twine 2.x" format.
This format can be imported into / read by: Twine 2.x application, TweeGo
<div id="store-area" hidden>
<tw-storydata name="The Story Name" startnode="1" format="SugarCube" hidden>
<tw-passagedata pid="1" name="Passage Name 1" tags="tagA">...</tw-passagedata>
<tw-passagedata pid="2" name="Passage Name 2" tags="tagB">...</tw-passagedata>
The quickest way to tell which of the two Twine GUI applications to use when trying to import an existing story HTML file isto open it within a Text Editor and search for tw-storydata If it's found then its the newer format else it's the older one.
Or if you have installed the TweeGo compiler then just use its --decompile option to generate a TWEE based version of the story HTML, it automatically detects which data format was used. This compiler can also be used to convert a Twine 1.x based project into a Twine 2.x based one, and vice versa.