I have the same problem. It happened after the update to version 4.3.21 of the plugin and later to version 4.3.23. After downgrading to version 4.3.20, everything works.
Hello. Thank you for this solution. This problem actually began after Facebook experienced their hours-long global outage. It was right after that, on October 7th, that I could no longer autopost to my Facebook timeline, page or group. I immediately opened a new support ticket here concerning it. Ludwig has yet to respond. I just updated my ticket to let him know that this temporary solution works.
Thanks again for figuring this out for us. Much appreciated.