We've heard that issue from a few other users recently. We're investigating, but so far, it seems like a bogus warning message. Can you tell me if the user account is properly created in Joomla? Mainly, that line is saying that there's an issue getting the user's email address from LinkedIn.
If, during regsitration, the account is created automatically (if auto registration is enabled) or the email is shown (during 'normal' registration), that means that the message above is being thrown incorrectly.
In that case, you can hide that message by setting the "Show LinkedIn API Errors on Front-End" to 'No'. Again, we're investigating why that message is appearing at all, but if it's not causing a problem, I'd hide it with that setting.
The Usermap area of JLinked simply shows you the Joomla user accounts that are connected to LinkedIn users. You should see a column with the user's Joomla user name and another column with the special LinkedIn ID that is assigned to that user. In the error message above, the user's unique id is "5BpMBfLK-r". There is no way to get more information about the user from the Usermap area. It simply shows you which of your Joomla users have a LinkedIn connection for them.
I hope that helps,
Alex
JLinked login error
