I suspect you are missing some variables in the extract script.
I would recommend going through the wizard for each excel file thats causing the problem just to test.
Pointing out the important parameters: you need to make sure the table is mentioned correctly:
(ooxml, no labels, table is Sheet1);
Also, make sure excel versions is exactly the same.
P.s. .xls uses biff whereas .xlsx uses ooxml, You cannot load an xls file with the ooxml addition, similarly, you cannot load an xlsx file with the addition biff.
Hope this helps.
Thanks a lot for your help. I've used the wizard with the problematic files, checked the ooxml vs. biff issue (it's OK). But the problem is still there. The wizard seems to recognize the chart with no problem, allows chosing the lable (i¡ve tried both with and without embedded labels), etc. (see detail below). Once I finish the process and start designing the file, the fileds are just empty, no data, no labels, nothing. I've tried to copy and paste the data of the excel file on a new excel file and sometimes it has worked fine but stil can't make it work with the original file wich has the same data and format.
[Compra o Venta],
[Valor de Compra],
(biff, embedded labels, table is [Detalle de operaciones$]);