Are you perhaps using an older version of DBMC, not Kodi? Find the System Info(rmation) entry in the System or Settings area (depending on the app and version).
If you are using DBMC, update to 16.7.00 via the DroidBOX Market app, then try again.
If you are using Kodi (17.3, if earlier, update via Google's Play Store), try typing the URL into the Browser app on your DroidBOX, see if it comes up OK.