Xelatex Fontspec Cannot Find Fonts

With setmainfont you're essential building case-sensitive font paths.

• Path=working directory for fonts
• BoldFont=filename segment of path
• ItalicFont=filename segment of path
• Extension=file extension of path

You're code does not work because you are telling fontspec to look in all paths like this (example shows paths for bold font):

/usr/local/texlive/2016/texmf-dist/fonts/opentype/GARABD.otf/GARAMOND.otf
/usr/local/texlive/2016/texmf-dist/fonts/truetype/GARABD.otf/GARAMOND.otf
/usr/local/texlive/2016/texmf-dist/fonts/type1/GARABD.otf/GARAMOND.otf
... any other font directory in your environment/GARABD.otf/GARAMOND.otf

TeX Default Known Font Path Segments

On Unix-based computers, you can figure out the TeX font folders with:

cat $(kpsewhich -var-value TEXMFSYSVAR)/fonts/conf/texlive-fontconfig.conf

which evaluates to /home/texlive/2016/texmf-var/fonts/conf for 2016, or for the appropriate year of your installed version.

Otherwise fontspec does have an automatic path finding mechanism for system fonts, where you can just do \setmainfont{Arial}, but this is not as explicit and therefore in my experience leads to problems with cross-platform or cross-computer compatibility.

See How do I load a texlive font with fontspec?

Empowering YOU to DO it Yourself

Find folder where you files reside (without knowing your OS, I will just make up something)

Given fonts are in same folder with these names:

/Library/Fonts/GARABD.otf
/Library/Fonts/GARAIT.otf
/Library/Fonts/GARAMOND.otf

How would I set up fontspec for this?

\usepackage{fontspec}
\setmainfont[%
  Path = /Library/Fonts/ ,
  UprightFont = MOND ,
  BoldFont = BD ,
  ItalicFont = IT ,
  Extension = .otf
]{GARA} % {contains only what is common among all file names (usually basename of font family)} 

---

Notes

Many pro fonts use dashes in their file names to separate the variants, so you'll often see the following:

/Library/Fonts/DejaVuSansCondensed.ttf
/Library/Fonts/DejaVuSans.ttf
/Library/Fonts/DejaVuSans-ExtraLight.ttf
/Library/Fonts/DejaVuSansCondensed-Bold.ttf
/Library/Fonts/DejaVuSans-BoldOblique.ttf
/Library/Fonts/DejaVuSansCondensed-Oblique.ttf
/Library/Fonts/DejaVuSansCondensed-BoldOblique.ttf
/Library/Fonts/DejaVuSans-Oblique.ttf
/Library/Fonts/DejaVuSans-Bold.ttf

How would i set this up? Well, unfortunately fontspec does not support all of those fonts simultaneously, so I might either settle for less and use \setmainfont or load them all by breaking them up into families e.g. \newfontfamily\dejavucondensed \newfontfamily\dejavu \newfontfamily\dejavulight.

\usepackage{fontspec}
\newfontfamily\dejavu[%
  Path = /Library/Fonts/ ,
  UprightFont = ,
  BoldFont = -Bold ,
  ItalicFont = -Oblique ,
  Extension = .ttf
]{DejaVuSans} % {contains only what is common among all file names (usually basename of font family)}