How do I overlay a report parameter value over a logo image on report header?

We are converting an in-house Crystal Report to Power BI Paginated. The client wants this where the report date changes monthly: 

I have tried to overlay a text box over the header image, adjusting the z-order to bring the text box on top of the image. However, when I run the report, the text box gets pushed into an open area, refusing to stick inside the yellow area:

Here is what happens when I run the report, the text box is pushed down below the image:

I have never observed this behavior in other contexts such as Access Reports, ASP.NET pages, etc. Since there is the ability to adjust z-order (stacking) I am thinking there is an obscure property which may help.