How can I add or change page permissions?
Please go to Heropost App on Facebook:
https://www.facebook.com/settings/?tab=business_tools
Please click on “Edit Settings” button. Then, you should click on “Business integration settings” and in the next page, click on “view and edit”.
You should select all the accounts and buttons and activate them.
Please activate all permissions available, including all accounts and even the ones you don’t even add to Heropost. It’s necessary because Facebook requires full permission on the app to work successfully.
Then try adding your Facebook pages or Instagram account in question again.