Maybe the folder string is still not correct? Your double quotes look wrong, as if you had written the line in Word and not in SED.

Aside from that, this seems just one of the usual problems that you need to solve when developing something. The way to solve it is eliminating one possible mistake after the other. First check if the font file is found at all at the path that you give. If it is found, but just not installed as a font, then the problem must be somehow connected to AddFontResource. Check if there are some conditions where it does not work.