Some people experience issues adding their Facebook Pages where after clicking the OK button in the window below:
Facebook redirects them to a list of their Facebook Pages rather than the correct window (below) being displayed in the Sked dashboard:
We believe this is caused by using a "business login". A while back (~2015 from memory) Facebook allowed users to create logins that could only view and access Facebook Page(s).
This type of logins is no longer supported by Facebook (from 2017 or so). As a result we cannot add Facebook Pages "based on" these no-longer-supported business logins.
You must be logged into a Facebook user account (that is a "person" on Facebook) that has administrator access to the Page (e.g. via Business Manager).
When you are logged in as a "person" you will see the name of the person in the top right corner of the Facebook home page: