There was email triggered on 13-11-2017 for which we can see the delivery(as seen in screenshot in my previous post). There was an email triggered on 17-11-2017 (also) for which we cannot see the delivery. From the screenshot below (for a different template) I see deliveries for every date which the emails were triggered. I don't understand the logic.
1. As it is a continuous delivery, one single delivery will contain all delivery logs for a certain period. By default, a new delivery is created at the end of week or month. In your recent screenshot, you can see have one delivery for one week. So, in the current case, since a delivery is present for 13th, any new emails might be accumulated as part of it (as 17th Nov is part of the same week.). If this is not the case then check point 2
2. Archival workflow is running or not? If the archival workflow is failing it will not pull all the recent data.
The archival workflow should have a name like "Message Center local Archiving" with the internal name "mcSynch_local". Note that depending on the instance, "local" can be replaced in these names by other external accounts name. For example: