error:PLG_SYSTEM_AUTOFBOOK_ERRORCODE_50

AutoFBook plugin is not a part of JFBConnect. I'm not sure what extension that is, but you should find their developers and ask them for assistance in helping diagnosing and fixing that error message.

If you feel the issue is related to JFBConnect, let us know why and we can try to look into it further, but I don't think there's anything we can help with on this issue.

Thanks,
Alex