When you get access to new Facebook Pages or you have restricted which Pages you are sharing with Sked through Facebook, you will need to use the "edit settings" option to change the Pages that are shared with Sked after clicking "add Facebook Pages".
To do this, click "edit settings" after you first click "add Facebook Pages":
Then when you go through the add Facebook Page sequence (detailed here), make sure that you tick all of the Facebook Pages you want to use with Sked when asked. This is the relevant step:
This will ensure that we can access the Pages from Facebook.