When attempting to update the plugin you get the following "Update Failed: Download failed. Unauthorized".
Make sure you entered the right key in the Gravity Flow -> Settings page and that a green check mark appears.
The reason for this is often that the license activation limit has been reached. You can manage your license activations in your account area on gravityflow.io.
If your server is on Windows, then you could be running into the maximum length of 256 characters for the file path and you may need to move your site to a higher directory so the paths are shorter. Here's link that might help.