This is a document created with a “future version” not a previous version. Perhaps we should clarify this message.
The document was created with Skyline-daily, which is our running beta release for Skyline 20.2, while you must be trying to open it with Skyline 20.1.
You can use Skyline-daily to open this file and the File > Share to save to the Skyline 20.1 format. However, information may be lost in the older format.
Hope this makes the issue clearer. Thanks for posting the message.