As you can see in the attached, the plain (default) theme when previewed in Settings shows the Item column. But when I preview a Purchase Invoice that I created, the Item column does not show. What am I doing wrong?
Doesn’t work with other pre-installed themes as well.
You need to post the edit screen for the purchase invoice
When I have an item such as Item A below with a code, a name and a description
I get this on the edit screen
but if you leave the code out, then you only get the description.
How have you setup your inventory items?
The guide Create and manage inventory items explains the use of the different fields.
Worth a read 
I have added an item that has a code to the Purchase Invoice and previewed it again, only the code column showed up. The item column is still missing. However, I have noticed that when I create a Purchase Invoice without adding a description to the items, the Items tab shows as “Description”. Any workaround to make both the Items tab and the Description tab show?
You are using latest version, I presume
The description always take precedence over the item name. There is no Item column, which leads me to ask what version are you using?
In the latest versions you have Code + Description or Description
@BernardAzar, do not expect any transaction to look like the sample layouts for themes. Those are images that only show the general look of the theme. They are not actual transactions. They only show representative columns. Notice, in this case, that column headings are different. This is because various transaction forms include different content with different labels. But themes are used for every type of transaction.
@Joe91 was right. Read the Guide.
