Thanks for your post. It is possible that your NVR is not compatible with FTP server connections or has some other sort of restriction/limitation. The standard way of using CameraFTP would indeed be to hook the cameras up directly, not through an NVR/DVR system.
You can first try reaching out to your NVR manufacturer support team to see what experiences they have with trying to connect with a third party cloud service. Otherwise, please email screenshots of your configuration pages to email@example.com so that our specialist can do their best to help you troubleshoot.