I don't know the error, but I thought it perhaps any network problem between itch.io and you, so I uploaded this game to my web server, may you try to access below URL.
http://doc1oo.lsv.jp/app/dungeonw2_07beta/
This game's HTML is about 2MB data size, so the loading time may be a bit long.
Game runs if I click the Link, itch.io has been having issues with HTML 5 and flash playing
