Calculating percentage change over month in Power BI

I am trying to calculate the percentage change over period of one MONTH of the subtotal of defective items in my dataset which looks like this:

Each record of ID_REG represents the SERIAL_NUMBER of a product that was deemed defective and I need to calculate the change in percentage of defective products for instance In May 2002 there were only 7 defective products in total and in April 2022 there were 10, this means a difference of 100*(10-7)/7

In order to calculate this measure I'm using the following DAX:

P_CHANGE_MONTH = 

    VAR __PREV_MONTH =
        CALCULATE(
            COUNTA('Sheet1'[ID_REG]),
            DATEADD('Sheet1'[Date].[Date], -1, MONTH)
        )
    RETURN
        DIVIDE(COUNTA('Sheet1'[ID_REG]) - __PREV_MONTH, __PREV_MONTH)

But I always get 0.0% no matter what I do, I always get 0.0% I have tried changing the date format and even the number of periods but it does not seem to work, look:

I want to be able to get a table like this one:

I have read some posts on the PBI forum, but those solutions never seem to work on my dataset.

You can do this in Power Query (Home=>Transform Data=>Home=>Advanced Editor)

If your query that returns the above table is named Table, then add a blank query and pasted this M code in place of the code in the window that appears when you select Advanced Editor:

let
    Source = Table,
    #"Added Custom" = Table.AddColumn(Source, "YearMonth", each Date.ToText([Date],"yyyyMM"), type text),
    #"Grouped Rows" = Table.Group(#"Added Custom", {"YearMonth"}, {{"Defects", each Table.RowCount(_), Int64.Type}}),
    #"Shifted Count" = Table.FromColumns(
        Table.ToColumns(#"Grouped Rows") & {{null} & List.RemoveLastN(#"Grouped Rows"[Defects],1)},
        type table[YearMonth=Text.Type, Defects=Int64.Type, Shifted Defects=Int64.Type]
    ),
    #"Added Custom1" = Table.AddColumn(#"Shifted Count", "perCent Change", each ([Defects]-[Shifted Defects])/[Shifted Defects], Percentage.Type),
    #"Removed Columns" = Table.RemoveColumns(#"Added Custom1",{"Shifted Defects"})
in
    #"Removed Columns"

• Create a column with only the YearMonth (yyyyMM)
  • I included the year in case your data spanned multiple years and you want to separate the values that way. If not, just format as MM
• Aggregate by Count (= Defects)
• Add a shifted column to the table
• Add a custom column with the percent change calculation

You can also do this with DAX

• Create a new table from your original data table
• Add a "first of the month" column
• Access the previous months value by using LOOKUPVALUE function along with DATEADD referring to the previous month.

New Table

Table 2 = 
    GROUPBY(
        ADDCOLUMNS('Table',"StartOfMonth", 1+EOMONTH('Table'[Date],-1)),
        [StartOfMonth],
        "Defects",
        COUNTAX(CURRENTGROUP(),"StartOfMonth"))

Add the Percent Change Column

Percent Change = 
    VAR prev = LOOKUPVALUE('Table 2'[Defects],'Table 2'[StartOfMonth], DATEADD('Table 2'[StartOfMonth],-1,MONTH))
RETURN
    ([Defects]-prev)/prev