Use the 16dec16 update.zip found on the forum. Use the local update option of the wireless update app.
For safety consideration, we now just release OTA update for android 7.0. And we do not suggest the users to use local update file.
It is not easy to understand the Blackview policy about updating to Android 7.0. It seems that many (not advanced) users have been choosen by BV to become nougat beta testers without even being asked for it and, on the other hand, many others advanced users that really like to test the new version cannot access to it. Is it really so or I am in an error?