Diagnosis
On the header overview, you have chosen a function for editing ordisplaying one or more header, but have not selected the header(s).

Procedure
Select the header(s) you want to edit or display. Either enter "x" inthe selection list or place the cursor on the appropriate line(s) andpress function key F9. Then choose your function again.
You also have the option of selecting all the headers in one step. Todo this, choose menu function Edit --> Select -->Select all.