Nothing like that happened here, both had 4 small files, namely Workbooks A,B & C and Test. Apparently columns D, E & F are not the same in length, but contain names of Employees which may or may not be repeated. Each column apparently represents one week, the workbooks came from various unnamed branches. The sheets appear to be consistent in layout, with Sheet 1 ("Operatori") I think it was...

Maybe if we are able to copy the three columns from each first sheet of each workbook to the Master workbook ("Test") and then create the unique list. if its Office 365 then it not an issue, if its another version then that's a bit more complicated.