Can't change time signature font

I’m using large time signatures on a big orchestral score, but the default is too wide, so I want to change the font.

I followed a video online and I click library-font styles-time signature plain font

Changing the font changes nothing

I click library-font styles-time signature font

Changing the font gives me boxes with question marks. I like boxes with question marks in Super Mario. Less so in Dorico.

What gives?

You also need to change the settings on the Time Signatures page of Library > Layout Options, to set Time signature design to Plain font.

Thanks dspreadbury!