Based on the output you shared, it looks like your server is not able to resolve the Dropbox API server host name(s). The Dropbox API servers host names are currently resolving correctly on our end though, so that indicates an issue with your DNS setup.
That is a matter of how your server and whatever DNS server you're using are configured. That's out of our control though, so I'm afraid I can't offer much more guidance. You'll need to debug your DNS setup. Specifically, you need to be able to resolve any *.dropbox.com and/or any *.dropboxapi.com host names.