See solution in other versions of Excel:
Before trying the following solution, you might want to make sure that you don't have any frozen panes that you need to unfreeze:
Learn how to unfreeze panes in Excel:
Question: How do I unhide column A in a sheet in Microsoft Excel 2011 for Mac?
Answer: Select Go To under the Edit menu.
When the GoTo window appears, enter A1 in the Reference field and click on the OK button.
Select the Column > Unhide under the Format menu.
Now you should be able to see column A in your Excel spreadsheet.