Are you talking about the Table View mode? If you added fields after the initial table creation then you will need to manually add columns (aka fields). If you click on any column you will see a submenu where you can select the other fields to add as a column.

You can also click on the funnel icon in Table view mode:

Then you can drag over fields that you want to add as a column. I only learned about this function years into my usage of Ninox. :)