Couple different issues mixed in your last post - I'll try to take them one at a time.
1. Updating older posts.
When WPBook Lite posts to your Facebook Wall (or the wall of a page/group/etc) it is a one-time event.
Updating that post in WordPress will not update the excerpt already posted to Facebook. I don't believe the Facebook API offers any way to "edit" things already posted.
If you want to re-publish to your Facebook Wall, you can edit the post, change its status back to draft, save that, and then publish it again - this will re-trigger publishing to Facebook.
2. Pushing comments from WordPress to Facebook
You mention commenting on the WordPress side and not seeing anything in Facebook. If you're using WPBook Lite, that is the expected behavior. WPBook would show that comment (which was made in WordPress) on the canvas page of that post, but neither WPBook nor WPBook Lite will actually push comments to Facebook against a wall excerpt.
3. Importing comments from Facebook to WordPress
The "number of days to check" is based on how many days old the Post is in WordPress - it looks for comments against Facebook wall posts for all the posts in WordPress published within as many days. Setting this to one will only look for comments made against posts published in the same day. (And this is publish date - so if you update a post and re-publish it but don't change the date, comments will not be sought).
As to why comment importing is failing, there are again multiple possible reasons for that:
- Your WordPress install does not have a functioning wp-cron - WPBook Lite and WPBook both rely on a wp-cron task triggered hourly to check for comments
- Your access_token is not an offline_access token because your Facebook app has the "deprecate offline_access" property set to enabled, which means your stored access_token is expiring, so when the import comments task runs it has no access to Facebook
- Facebook's API stops responding. This happens less frequently now, but does still happen from time to time. Sometimes this is network issues between your server and Facebook, sometimes it just drops a response.
- Your WordPress install runs out of memory or the process is shut down by your host. If you're checking for comments on a large number of posts, the WordPress wp-cron process can time out, run out of memory, or be shut down by your hosting provider.
To see which of these it is, enable debugging (setting in WPBook Lite settings page) and look at the debug.txt (separate file from the one for publishing) to see what it says.