Another potential cause may be the formatting of text ... box so that the cursor changes to a double arrow as in the snapshot directly below. Then hold the left mouse button and drag the column left ...

Click the empty cell underneath the column of numbers that you want to add up. Or, if you want to sum a row of numbers ... You should see Excel draw a selection box around the numbers to be ...

You can use the Sum function in Microsoft Office Excel to sum columns of data, whether your data is in an Excel table or is simply a range in a column of your worksheet. The sum of a column of ...