I would be very greatful if you post your fix when you have it.
I am having the same issue, 'Invalid Scopes: manage_pages' error. I have read all posts that I can find relating to this issue and can confirm the following:
1. we have a vaild ssl
2. we are using the facebook page id not the profile id.
3. 2 factor authentication is off
4. we have the most recent version of JA Social Feed (1.3.6)
I can see that the Facebook app page gives you an option to do an App Review, which allows you to add manage_pages to it. Is it necessary to complete this?
If so, are you able to provide us with the information required? (see attached)