Can you verify the following:
* You have the JLinked System plugin
* In the Social Configuration area of JLinked, under the Misc tab, if you've set an "Admin Render Key" that you are using it in the tag, like {JLinkedLogin key=1234} (if your key is 1234). Alternatively, you can remove the render key.
Let me know if that helps or still doesn't work after the changes.
Thanks,
Alex