Error when registing a new user: Please enter a valid email

I'm not sure what would be happening there. It appears that you're still using JFBConnect v4.3.4, which is over a year old. Facebook's interface changes constantly, which is why we're always releasing new versions. The latest from us is v5.2.1. It's likely that Facebook changed something that v4.3.4 isn't compatible with, but I'm honestly not sure. We don't test with such old versions.

My only suggestion here is to upgrade to the latest version of JFBConnect.

Thanks,
Alex