Project doesn't have valid binder structure file?

Okay, so I was trying to sync my Scrivener projects from my iPhone to Dropbox. (NOTE: I do not have ANY other devices attached!!) It didn’t exactly work, so I think I just stopped trying to sync it. But on one of my projects, once I tried to open it, said: “The project cannot be opened because it does not contain a valid binder structure file.” I have no idea what to do! How do I fix it? Once again, I have no other devices connected! Just my phone!