There was a bug in the v4.3.1 release. We actually just released v4.3.2 of JFBConnect to fix that issue. To fix, either enable the JFBCSystem plugin (which will get rid of that error) and then on the Overview page you should be able to automatically update. The auto-update may not appear for a few hours as it can take some time for it to refresh it's data.
Alternatively, download the new v4.3.2 zip file from the My Subscriptions area and install that.
Sorry for the inconvenience, and hope that helps get you going,
Alex