You need to include the list of columns in the GROUP BY clause which are available in the SELECT list and doesn't associated with an aggregate function.
Your query should look like-
SELECT sum(Column1) As [Item Price],[column2]As [Item Name],[column3]As [Table Name],[Flavours],[Customer Name],[Delivery Time],[Time] FROM Runtime Group by [column3],[column2],[Flavours],[Customer Name],[Delivery Time],[Time]
But the result you will get probably is not what you expected. You need to include only those columns which are essentially needed.
Please let me know with a sample output in that case so that I can help further.