That's a bug in JFBConnect. We have some code that used to be required to work on https sites to prevent mixed-content errors. That code is no longer required and causes the image to not display. This will be fixed in the next release.
To fix now, edit the /components/com_jfbconnect/libraries/provider/linkedin.php file. Around line 123, you'll see:
if ($scheme == 'https')
$initJs .= "IN.Event.on(IN,'frameworkLoaded',function(){if(/^https:\/\//i.test(location.href)){IN.ENV.images.sprite='https://www.linkedin.com/scds/common/u/img/sprite/'+IN.ENV.images.sprite.split('/').pop()}});";Delete those 2 lines and you should be good to go.
I hope that helps,
Alex
[LinkedIn] Error with LinkedIn Icon
