Conditional Cumulative (Running) Total Measure - Do Not Calculate or Display If...

Problem: Trying to create a cumulative / running total measure that will only calculate if data for the specified or selected time frame is available. Measure is expected to change based on slicer selections: (1) Survey Month (2) Entity

Current State:
For the month of September (month 1), visual and calculation are displaying counts as intended.

For October (Month 2), no data has been submitted yet. So monthly counts at 0 are correct. But cumulative amounts are intended to be 0 as well, as cumulative amounts should only show if data is reported for that given month.

I've attempted a measure like this. Upon drilldown to the entity level, it works as intended. E.g. It'll show only the entities that reported and their monthly and cumulative amounts. But at this "staff type" level, I just can't get it to work:

Monthly_Hire =
CALCULATE (
    SUM ( 'FactTable'[Value] ),
    KEEPFILTERS ( 'FactTable'[Attribute (New/Proj)] = "New" )
)

Cumulative Hires =
IF (
    SELECTEDVALUE ( 'EntityTable'[ReportStatus] ) = "Not Reported",
    BLANK (),
    CALCULATE (
        [Monthly_Hire],
        ALLEXCEPT ( 'EntityTable', 'EntityTable'[Entity], 'EntityTable'[Entity-Month Key] ),
        'EntityTable'[Month Sort] <= MAX ( 'EntityTable'[Month Sort] )
    )
)

Sample Data

Could not include full sample data due to character limit, but this should be sufficient.

Entity Table

FactTable

Expected Result

Probably not the best illustration of the expected result. But as you can see, only Entity A reported in October. Therefore, only their cumulative counts appear.

Sample data included above.

Connected as 1:* (Board-Reported Key to Board-Month Key)

Appreciate any help I can get on this!

Thank you