Missing Time Report does not work correctly if there is no resource availability.
For example, the week on the report should display a total of 40 Available hours per resource, but instead it is only showing 16 hours.
Set the DAILYRESOURCEAVAIL slice back to cover at least the entire time period of your report. In the example mentioned here, the 16 hours are getting calculated becuase this slice is set to Start on a Thursday instead of the first day of the week. Since for this week, an availability time slice only exist for Thursday and Friday, this is where the 16 hours are coming from.
Note that the DAILYRESOURCEAVAIL slice rolls over monthly so make sure you set it back far enough to cover the monthly rollover.