DataTables displaying blank cells but the rows have data

I am having a problem with the DataTables plug-in for jQuery.
I am loading data with a JSON, but only some columns get their values displayed (see screenshot below).

No values being displayed for the three right columns

However, I printed the selected row from Datatables with console.log(table.row(this).data()) and the print shows that there is data for the columns that appear to hold no data. Furthermore, right I am setting the "defaultContent": "", but if I set it as "defaultContent": "Not set", DataTables displays “Not set” for all those blank values, which is expected, but means that somehow it is not reading the content from the rows. Please check the next screenshot with the console print with data on columns “Un.”, “Quant.”, “Total [€]”.

Console print on the client showing that the row holds data for the columns that appear blank on the table

Has anyone gone through this?