I would recommend trying to create a new FB or Twitter Channel to see if it's able to autopost. I'm unsure what version of JFBConnect you were upgrading from, but v8 introduced a lot of changes for posting content, mainly for Facebook, but some minor changes for Twitter.
The new channel can connect to the existing Facebook Page, so it'd be a complete duplicate. If it works though, you can remove the old channel and just stick with the new.
I hope that helps get you started, but if not, please let us know what else you've tried. The autoposting and manual posting use the same logic, so beyond the above, please let us know what type of content your autoposting. I'm assuming Joomla articles/content, but if not there could be an issue with the integration with another extension.
Thanks,
Alex