Please note that Zoho Sheet leaves a green mark in between rows/columns if one or more rows/columns are hidden in between.
1. To unhide a row or a column, hover over the green mark.
2. Click on the arrows that appear when you hover over the mark to Unhide rows or columns.
3. Alternatively, you can go to the View menu and click on the Hide & Unhide option.
4. From there, choose to unhide the rows and the columns that are hidden.