Sometimes while deleting variable mappings in CastIron studio, that particular activity becomes corrupt. By corrupt I mean, not all variables would be displayed correctly - hence we cannot do mappings to these variables.
How to avoid this?
Only delete variables that are in the bottom of the mappings. Do not delete variables that are in the middle.
How to correct if an activity is already corrupt
Since this is only a display issue it can be corrected easily. Right click on the activity and copy it. Then paste the activity again into the orchestration. The pasted activity would have all the variables in the mappings displayed properly.