The Security error message is shown when Jump thinks it is not connecting to the same computer Jump Desktop was configured on. As a precaution it does not allow you to connect.
To fix this, you'll need to force Jump to rediscover your computer. You can do this by deleting your computer from Jump: Open Jump and swipe your finger across the entry for your computer, then tap the Delete button. Next press the home screen button and restart Jump by tapping the Jump icon. After a brief wait you should see your computer reappear. Tap the computer to reconnect.