Demand Notice: Challan is not available for the AY

I have received a demand notice with the following reason "Challan is not available for the
AY". I paid Self assessment tax which is showing in 26 AS and also mentioned the challan details while submitting ITR but the same was not picked up during processing. Please confirm if i have to select "Demand is correct" and enter challan details or "No, demand is not correct" and enter challan details.