I have a bunch of older projects that are marked as Zero Bytes

[Vincent_Vincent]

Both of these seem like viable fixes. Issue successfully resolved in both cases.

MacOS Scrivener - Zero Length Data error - No syncing

I followed the instruction here: To make an online-only file available to open in third-party applications: 1. Open your Dropbox folder in Finder. 2. Right-click the file you want to have available. 3. Click Make available offline. 4. The file will be downloaded within your Dropbox folder and can be opened through any third-party application. Once an online-only file has been downloaded in Dropbox, you’ll see the cloud icon change to a green checkmark. to make the problem file available…

None of my files will open now: "The project seems to be of an older format,..."

You might want to check with Dropbox support. My best guess would be that you have “smart” syncing turned on, which causes the Dropbox app to only download files as needed. That’s known to cause big problems for Scrivener. Downloading through your browser forces Dropbox to give you the whole directory – a Scrivener project is actually a folder, with subfolders and potentially hundreds of component files – which is what you want. Katherine