Do you have an appropriately stored access token?
On the WPBook settings page (WordPress -> Settings -> WPBook) there is a "Generate Access Token" link, and underneath that it should say something like this (your tokens and page names will vary of course):
That will trigger a multiple step process which will generate an access token and store it - you should see your blog home page load with a message at the top declaring success or offering an error. Revisit this page and you should see the access code stored below:
Stored access token = AAADzraCG2leWjZCRhLFjdZCWXUlZCNyQFFdUtj6ulp2Eel5an7OA9cqALjCZA0KWXiYvZCWZAaJb2Cr56k4VIxeoZD
Note: If you already have a stored access_token, you should not need to generate a new one, but you can if need be - it won't hurt anything. This stored access_token is required EVEN IF YOU DO NOT PLAN TO POST TO YOUR PERSONAL PROFILE WALL
Permissions for pages
This section will cover permissions for posting to pages.
You've indicated you wish to publish to this page: 44061748871
An access token corresponding to the page titled WPBook has been stored.
It is AAADzrTzlu0kBAILcKE6TJ5zxU7FfH7l27dPDPJlTPng4gASDASD2LreRFIeCjfeqahdwZBTtNhO1UJBmdpcKFblFAMg41vuFc0hxuvwZDZD