OOALV PAI problem

Hi All,

I am new to OOALV. I am done with my report. But when I am trying to download the report output to a local file or excel sheet. from standard ALV download option. I am getting a runtime error saying " Field Not Assigned".

I checked in SDN also but no use. I did not found any solution. every body is telling error in Field catalog. But I checked twice there is no error in the FCAT.

Please suggest. Thanks