When you say they are not visible, do you mean the cell is completely blank
or that you see #######
If the cell is blank, perhaps the font is the same color as the sheet?
Change the font to any other color.
If you see ########, point your arrow between the column in question and the
column to its right until you see arrows pointing away from each other, then
double-click your mouse. This will auto-size your column to best fit.
