DAX measure multiple tables - problem

Hi, I am having problems with a visual (below) not working correctly when a slicer is applied.

Data tables:

Table 1: Calendar (contains dates on axis below and also when a calculated column listing a '1' when a date is a working day) (relates to Table 2 1- *)

Table 2: Financial table containing this example revenue data in graphic

Table 3: Account Key (this relates to Table 2 1- *)

This visual below tracks revenue from Table 2 across date axis (table 1).

The red line is a measure called Run Rate - this is a revenue figure (table2) divided by the number of working days per month (table1).

Problem:

when an account is selected from a slicer (table 3) this measure does not track across the time axis, instead only showing a value in Jan. 

This measure is: