Aggregate + month function

hello as the title would like to combine the works aggregate with month.
The proven formula does not give me the desired result
In the attached file in the sheet2 I would like to have the search result by month of the date in A2
In column B I have inserted a formula that does the research correctly for a single day but, if possible, I would like it to do it by month.
Then report the data that is filtered in the sheet1.
Thank you

Sorry I found the solution
it was a question of brackets

= IFERROR (INDEX (Sheet1! $ D $ 5: $ D $ 959; GATHER (15; 6; (ROW ($ A $ 5: $ A $ 1000) -4) / (MONTH (Sheet1! $ A $ 5: $ A $ 959) = MONTH ($ A $ 2) * (Sheet1! $ D $ 5: $ D $ 959> 0)); ROWS ($ 1: 1))); "")