contact infomation can not be displayed.

I want to change the order of firstName and lastName on PDF invoice.
so I’m trying to use values of $contact.firstName $contact.lastName
but the following information can not be displayed although it is listed in the contact column.


$clientDetails and other value is works fine.

I use selfhost v4.5.9

Have you tried creating a test invoice, it may just be missing in the preview.