Not showing zero values when date filter applied

Can anyone think of a reason why a datetime filter applied to a report causes a visualisation not to show zero values?

A have a table showing monthly contract revenue (vales) by asset (rows)  by month (columns). Some assets are new so dont have any contracted revenue to show yet. If I apply a datetime filter on the report or page to show data for present day onwards i.e. remove old information I lose any assets from the tables that has zero values.

I first thought that it was because I removed blank values, however found that it was in fact as soon as I apply any kind of filter by date.