If you are having problem posting surely that’s a bug from facebook token validation, that’s one of the security feature added by Facebook last October 2018. In order to fix that, all you have to do is refresh/update your Facebook account that was connected on FBGapp.
To do this, follow the guide below:
Goto Settings > Facebook Accounts > Update (the middle button on your profile picture).
Or if you are using browser you can simply go here “https://fbgapp.com/en/settings/fb_accounts“
Simply remove the account and add again (Note: This will automatically invalidate all running schedules).