Gimp 2.8.22 refusing to load font

[Ofnuts]

Two possible solutions:

1. Install the font for Gimp only, by putting the TTF in the fonts directory of your Gimp profile.
   
2. Have Gimp rebuild its own font cache (see here for where it is, in your case, just erase everything).
   

You may have to combine them because even if you install a Gimp-specific font the old cache contents may mask the new version.

If I had to place bets, Gimp is more likely to notice a new font version if the font file is in your Gimp profile than if the file is installed for Windows (in that case, Gimp doesn't really know which file it comes form and so cannot determine if this is a new version).