This happens on account changes on the registry, or local system changes.
Most common: Switch from wireless to wired connection or back.
The solution to fix this, is to delete the saved login, and reuplink, to update the saved credentials.
If you have a saved login, please delete it:
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click on the white x in the red box.
Now click on the "Change Uplink" button and enter the credentials you use on our [[ http://registry.star-made.org | registry site ]].
You should be able to connect to servers again.