Valid binder structure file?

What does this mean? The project is opened quite happily on Windows Scrivener and was open on the iPad yesterday.- so what happened? And how do I fix it? Thanks

It most likely means that you didn’t wait for Dropbox to finish syncing on Windows after editing it there before trying to open the project on iOS. Make sure it’s all synced on Windows and then try syncing on iOS again. A .scriv project contains many files, so if you sync on iOS before they are actually all available on Dropbox (because your desktop machine hasn’t finished syncing them), the project may be in an invalid state.

All the best,

Keith, thanks - and that is exactly what it was.
I wonder if it would be possible to hint at this in the error message. The message as is just freaked me out, it was as if something key had just disappeared. A guiding hint would have gone a long way. As it turned out, beause I’d done some major rearrangement in Dropbox it was taking an age to sync from Windows, but this wasn’t obvious to me.
Thanks again.