How to use Font Effects/Small Capital with a custom font

I recently installed a font from Google fonts, that I need to shoot a video with, Dosis. The text I am working with will need to be formatted in Small Capital letters, so that it comes out easily readable after recording, and close enough to the logo of my partner.

I was hoping to use the Font Effects/Small Capital function in Writer, which does the job perfectly with all other fonts but I can’t seem to make it work on this one.

Any clue?
Any help to save me from manually setting the font size of each sentence’s first letter would be greatly appreciated.

Edit: Applying the effect on a different document actually worked. Could it be some characteristics of the document, or maybe a bug? The original formatting of the two documents is actually totally similar.

Variable installation of Dosis font works in LibreOffice Probably, the original poster needed to install the static version of the font in 2015, rather than the variable.