Borders not appearing on keycaps or responding to css

[Nesbeth22Kopf]

Example images of the Virtual Keyboard show a border on the bottom of the keys. I don't see this border in the demo or when I implement the keyboard. I have been attempting to customize the color of the border according to documentation at: https://cortexjs.io/mathfield/guides/virtual-keyboard/
I have been setting values for:
--keycap-border
--keycap-border-bottom

Setting others styles has worked for me in all cases except for these border styles.
These don't seem to affect the absence of a border, even when I set a border weight and style. Am I misunderstanding the purpose of the border styling? Is applying a border around the keycaps possible? Thank you for your trouble!