/setmainfont Error on path 2 levels deep?

Question

I am trying to house all my customizations and fonts in an asset folder so I can use it on multiple documents and maintain the same styles. Unfortunately whenever I try and put the fonts into a path two levels deep I can't compile the document. I get the error:

! error:  (type 2): cannot find file ''
!  ==> Fatal error occurred, no output PDF file produced!

Below works:

\newcommand{\fontmercury}{\setmainfont[Path = ./fonts/,
  BoldFont=mercurybd.ttf,
  ItalicFont=mercuryi.ttf,
  BoldItalicFont=mercurybi.ttf
  ]{mercury.ttf}
}

This does not work:

\newcommand{\fontmercury}{\setmainfont[Path = ./assets/fonts/,
  BoldFont=mercurybd.ttf,
  ItalicFont=mercuryi.ttf,
  BoldItalicFont=mercurybi.ttf
  ]{mercury.ttf}
}

The path is correct, it just generates an error anytime I go more than one level deep.

EDIT: I figured it out. It was the cache problem discussed here. Deleting the otl folder in my case allowed it to compile. LuaTeX cannot find existing font

Answer 1

In addition to deleting the out-of-date otl directory, you should also consider using a different setup for \fontmercury. The fontspec package provides the \newfontfamily directive. For the case at hand, using \newfontfamily would seem more efficient than issuing a \setmainfont directive. You could insert the following instructions in the preamble:

\newfontfamily{\mercury}{mercury.ttf}%
      [Path           = ./fonts/,
       BoldFont       = mercurybd.ttf,
       ItalicFont     = mercuryi.ttf,
       BoldItalicFont = mercurybi.ttf]
\newcommand{\fontmercury}[1]{{\mercury #1}}

Then, in the body of the document, you'd write

\fontmercury{...}

Answer 2

I figure I would post this as an answer since I am not sure how to mark this as answered. But I figured it out shortly after posting. I use TeXLive + TeXWorks. So I deleted the otl folder in the path C:\texlive\2017\texmf-var\luatex-cache\generic\fonts\otl. It worked when it came to building the doc after.

More details: LuaTeX cannot find existing font