Not able to change fonts

I'm just bought my next ebook (epub). Sent it to my Kobo using Calibre. Opened it in Koreader and tried to change the font to Noto Serif, but nothing happens. No matter what font I choose, it doesn't change. Status message says something like "Redrawing font to Noto Serif" (or whatever font I choose).

Any ideas? Didn't have that problem with my last ebook.