After donation, received donation key as attachment. The key is then saved in mac Documents directory with file extension .cyberducklicense as ending. When double click on the license key, Cyberduck program launch with error message as pop up information windows "Not a valid donation key"
Make sure the donation key file is not modified when saving it from your email application.
* If you are using a webmail provider, try using a different browser or email client application to access your mail.
* Forward the mail to a different mail account where you possibly don’t have an issue downloading attachments.