A number of users are reporting problems which seem to be caused by changed Facebook application settings.
In your Facebook Application settings, there is an "Advanced" set of settings with a "migrations" section. For WPBook Lite to work, current recommendation is:
- "Deprecate offline_access" must be "disabled" - if this is enabled WPBook Lite will not be able to do much of anything.
- "Enhanced OAuth dialog" should be disabled - this one I haven't tested very thoroughly, but I know it works with this migration disabled and at least one user has had trouble with it enabled.
I believe those are the only settings you would need to change, but it is difficult to keep track, as Facebook Applications created at different points in history have different settings available.
After changing your Facebook Application settings, you will need to return to WPBook Lite settings page in WordPress, validate that your app_id, secret, and profile ID are correct, save those settings, then return to the WPBook Lite settings page and regenerate your access token.