Accumulated values for Cohort Visualization

Hi Everyone, I'm Trying to make a Cohort Viz, but something has been bugging me for a while.

The table i'm using has client data, so i am not able to share it. But i'm dealing with users that has to pay monthly fees, and one of its visualizations is the Churn Cohort, which means is the people that drops out of the contract.

Its rules goes as follows:
Whenever someone drops out of the contract, check the month the user dropped, and check which parcel the user dropped. The user will then be accounted for in these 2 criteria, as shown above.

But, i want to transform the measure into a Accumulative Measure, but I am not pulling this through.
the visual i'm looking for is something like this:
.....
Date = M1 | M1+M2 | M1 + M2 + M3 |  . . .  | Mn 

What am I doing it wrong in here?

Here's the measure:

Cohort Churn = 
VAR primario = 
    CALCULATE(
        [qtd_mensalidades],
        FILTER(
            fMensalidades,
            [mes_venda] <= TODAY() &&
            [numero_mensalidade] = DATEDIFF([mes_venda], [mes_devolucao], MONTH) + 1 &&
            [status] = "Devolvido"
        )
    )

RETURN 
 primario 

for some info about the table:

[month_sold] is the month the user signed the contract
[month_dropped] is the month the user dropped out
[parcel_number] is the number of the parcel of that entry.
[status] is the status of that user. can be dropped, active, late, etc.
The table has data of all the parcels the user has to pay, so in example:

the user 90182 signed a contract, now in the database it wil be created automatically all the parcels and thates the user has to pay, something like this:

in this scenario, the user would be in accounted for in Dez 2024 in Month 3.