For some reason, your DAS registry setting might have become corrupted. Here's how to fix it:
- Launch the Jalview desktop (IMPORTANT: if you have more than one instance running already, close all but one).
- Go to the Tools->Preferences option to open the preferences panel.
- Open the 'DAS Settings' pane in the preferences panel - if you can't see it, click on the right most tab ('Editing' in my screen), and then the '>' icon to scroll to the next tab along.
- Replace the existing URL in the 'Use registry' text box with: "http://www.dasregistry.org "
- Click 'Refresh Available Sources' - you should see lots of sources appear in the list
- Hit OK in the preferences dialog box. This saves your preferences.
- Shut down Jalview, and then start it again and open the 'Fetch Sequences' dialog box to check that you can see all the sequence databases.