Custom duplicated panel card layout appearing blank on Redwood

Summary:

On the Account object, we are currently using the standard Opportunity template along with the standard panel card layout, which displays four fields.
To add a fifth field, I duplicated the standard panel card layout and made the following changes:

Updated the style from widget-card to label-card, in order to add fifth field

However, after previewing the updated panel card layout, I observed that:

The custom layout is not being applied.
As a result, the panel card appears blank in the UI.

It seems the layout mapping is not functioning as expected after the style change and field addition.