category cannot be null row: 3 sheet: OPTASK

Honestly it would be more helpful to upload your spreadsheet. Barring this, can you clarify if you checked the spreadsheet's line 3 or the contents line 3 (which are sometimes more like line 5 or 6)? Have you also tried copying what you're trying to kickstart into a "fresh" (empty) kickstart file? (sometimes mine get corrupted and then they are just useless)