Hi,
First try to see the fields which are part of your data source.
Use ECC Table - ROOSFIELD, use your data source name and display the table data.
see the fields which are there, in that if you see requried field was exist then you can see the column SELECTION.
if selection is A then your field will be hidden by SAP. Thru small abap we can make it as visible.
Even check this table - TMCEXCFS ,enter your communication structure name(MCXXXX)
if your filed status - F(disallowed) then theu abap code we need to make it state as A(Active).
Thanks