error trying to use vba countifs function

I have two workbooks

i have this code which gives me an error

Junk1 = Application.WorksheetFunction.CountIfs( _
study_number_range, Workbooks("To_be_used_with_macro1_doc1.xlsm").Worksheets("Sheet1").Range("A2"), _
Received_col_range, "<>" & "", _
Closed_col_range, ">=" & start_date1, _
Closed_col_range, "<=" & end_date1)

any idea why it does not work?