UPDATE: 12/10/2018
We appear to have a handle on this issue and our tests with FTP functionality show that it is working properly. Please try the FTP upload process again and use the test delivery option from the Product Detail page to ensure it is working for you.
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We are continuing to have issues with files uploaded via FTP and are working to resolve them. Any file less than 2GB in size should be uploaded using the website interface until this is resolved.
Developers are working today to resolve the issue, but may not have a solution live until Monday morning.
If you absolutely need to get a larger file attached to your product, then use the following workaround:
1. Upload your file to any public file location such as your website and make note of the web address to access the URL. If you upload your file named "myfile.pdf" to "yourwebsite.com", then the file URL should be http://yourwebsite.com/myfile.pdf.
2. Click the "Change File" link from the Product Detail page in your account and scroll down to the bottom of the page and use Option #4.
3. Enter the URL from step #1 in the text field and click the "Update" button.
5. Test to ensure the file attaches properly.
This workaround should provide the minimum needed functionality to sell your file. It should be reverted back to the FTP upload when we get it fixed on our end and the file should be deleted from your web location.