Zip file uploaded to Database Exchange does not contain a valid upload format

I am using Amazon S3 to store zip files which are then uploaded to Database Exchange. When I try to validate the URL I obtained from the S3 site, I get the error message, “Zip file does not contain a valid upload format”. Lots of other files have worked perfectly using identical procedures. Any ideas as to why this one might not work?

The Database Exchange wizard downloads the zip file on your computer and looks inside to make sure there is a .pandb file with the correct name. If it doesn’t find the file, you’ll get that error.