How to authenticate / re-authenticate
It sounds like somehow we didn’t get the app permissions when you authenticated Facebook. Please remove all Facebook and Instagram accounts from within the software and remove the software app (Campaign Share) from your 'Business Integrations' page in your Facebook account, then re-authenticate in the software. Be sure to check all the permission boxes. It should clear this up.
Be sure that when you go to add a second Facebook account, you log out of the first Facebook account by going to www.facebook.com and clicking Log Out from the menu (Otherwise, it will just keep trying to add the first account), then return to your Account Preferences in the software and add the next Facebook account, repeat for each new account.
Also, make sure that the Facebook account you authenticated with has an "Admin" or "Editor" role. The following roles will not have permission from Facebook to post: "Moderator", "Advertiser", "Analyst", or "Jobs Manager".
Here’s a video on what to do: