Get Desired Size using Force Layout Prepass Returns 0

I am unable to get proper Desired Size for a Widget, after Calling Force Layout Prepass


The small white bars are buttons, with an overlay as child of the button and a spacer added as child to the overlay. The spacer size is set to 2.0x0.0

The Buttons Vertical Alignment is set to fill (which as you can see in image, makes the button the height of its container

I have a text widget that displays text associated with the button on hover, and I need to get the height of the button to properly offset he position of the text widget when thebutton is hoverd, so that its position will be above the button.

However, the desired size returns the size of the spacer, not the size of the button widget.
This is the blueprint code for the Button

I don’t understand why I am not getting a proper size, when the button is clearly not a height of 0