Hi CBeeC.
You didn't include what you have tried to do to unhide the rows or columns, so I'll start with the options to do that.
- You must select rows or columns on both sides of the hidden ones by clicking on the Row numbers or the Column letters to select the entire rows or columns. You can drag those to select the range on both sides. It may be easier to just select the corner square that selects the entire sheet because you won't have to determine which rows or columns are hidden.

Then right click over either a Row number to unhide Rows or a Column letter to unhide Columns and choose Unhide from the menu.
- On the Home ribbon in the Cells section click on Format and in the menu select 'Hide and Unhide". That will open up a side menu where you can select Unhide Rows or Unhide Columns. Click on them to unhide the hidden Rows or Columns.
