Matrix Values are not Affected by Date Slicer

Greg_DecklerAfter reading more similar posts, I think my error is not referencing the related table within the formula...but I'm still lost on how to make it work.  Here's what I have so far:

Table 1 - has IDs and dates (ocurring multiple times)

Table 2 - has column of unique dates and the month in text

Table 1 & 2 are related by their date columns, Many : 1

I have two measures:

1) Count of IDs = COUNTX (FILTER ('Table_1', 'Table_1[ID] > 0), 'Table_1'[ID])

2) Filtered by Month = CALCULATE ('Table_1'[Count of IDs], ALLSELECTED ('Table_2'[Month]) )

Visuals:

Slicer - Table_2 [Month]

Matrix - Table_1 [ID] as Rows; (Measure 2) 'Filtered by Month' as a value

How can I get the Month selected in the slicer to filter the Measure 2 values for only that month selected?

EXAMPLE...

SLICER

January  February  March  April               ------->           January  February  March  April

MATRIX (No month selected in slicer)                          MATRIX (January selected in slicer)

 ID      Measure 2 - Filtered by Month      ------->          ID      Measure 2 - Filtered by Month

 1.1        1                                                                        1.1        1    id 1 only showed up in Table_1 one time for January

 2.7        1                                                                        6.5        2    id 6 only showed up in Table_1 two times for January

 6.5        3                                                                                            ids 2.7 & 9.1 didn't show up at all for month of January

 9.1        2