Full size Add button not appearing on Form view

[Nick_O]

First timer here,
I’m trying to basically re-create the sample Order Capture App. When I hit the “Plus Sign” to create a new order, I’m missing the “Add” button to the order line items. See screenshot.

The strange thing is, when I get out of the order form UX and into the Order Detail UX, the order line items are there. So my reference appears to be working, but when the order line items are blank (which they would be everytime you create a new order), the related records field is missing.
Any help is appreciated.