Why aren't new comments from Facebook posts or ads being added to tickets?
The Facebook integration will only pull in comments from standard wall posts for one week after its creation. Any comments added to a standard wall post more than a week after it is created will not be added to the original ticket, nor will they create a new ticket in your account.
When Facebook ads are converted to tickets, the integration will pull in any comments added under the ad up to a year after its initial creation, as long as the ad's ticket is still in an editable state i.e. not Closed.
Any comments that have been added to your posts after this will still exist on the post on Facebook itself, but they will not be pulled into Zendesk via the integration.