Getting null values instead of actual values when blending data

[Cherise_Bugeja]

Hi, I am blending data and using left outer join, however I keep getting null values instead of actual values. As far as I'm concerned null should only appear when the value is missing or 0, however in this case I am supposed to be getting a conversion rate in %. What am I doing wrong? 

As can be seen in table 1, I am measuring exits (metric) and using the event_label (which is the name) as the dimension.
In table 2, I am measuring the pop-up views (metric) and using the event_label (which is the name as the dimension).

Then I am using left outer join and using the event_label field to join both tables.

Then in the set up section of the new chart I am using event_label as the dimension and added the new conversion rate metric using the formula: SUM(Exit From Pop-up) / SUM(Pop-up Viewed).

Despite, this the values for the conversion rate are still being shown as null, when in reality there should be percentages displayed.