I'm afraid the core problem is the font metadata. The AGauge/CGauge bits should never have leaked in the font face name. While many font editors let font authors put pretty much any string they want in the face (style) field, in practice there are strict rules to respect if you want applications to make sense of them.
A few years ago Microsoft got serious about using css-like styling for its apps and got bitten by all the fonts with inventive naming out there. So they wrote strict guidelines about what could actually work in apps, with buy-in from Adobe and other major font players (Note that Microsoft is co-maintainer of the OpenType spec and uniscribe is pretty much the reference OpenType engine). Your font does not respect those guidelines
Please read the Microsoft whitepaper. It describes the kinds of font naming Microsoft manages to salvage, the heuristics used, and the canonical names the heuristics produce. A good font will not hit those heuristics because its naming will already use the canonical forms and need no correction. A bad font will at best have its naming silently corrected on a Microsoft platform. On other platforms such as Linux or OSX there will be no correction so wild naming will produce wild results, including the failures you hit.
https://blogs.msdn.com/cfs-filesystemfile.ashx/__key/communityserver-components-postattachments/00-02-24-90-36/WPF-Font-Selection-Model.pdf http://blogs.adobe.com/typblography/typotechnica2007/Font%20names.pdf
For example, your fontconfig output shows ReykjavikOneCGauge.otf is declaring either ReykjavikOne OT or ReykjavikOne OT CGauge (in that priority order) as family names, and CGauge as face name. According to the Microsoft whitepaper CGauge is not a valid face name so the font should have used ReykjavikOne OT CGauge as family name, and build a face name from the appropriate WWS (Weight Width Slope) qualifiers. Unfortunately for you, it declares ReykjavikOne OT (without CGauge) as primary name, and CGauge as useless face name.
Note that older software does not read those new Opentype naming fields, so regardless of what the author puts there, it may sort of work as long as your font stack is ancient enough.