Couldn't figure out why Montserrat-ultralight wasn't loadking.  Then found this in the child theme's custom.css

src: url('http://thegem-wptheme.loc/wp-content/themes/TheGem/fonts/montserrat-ultralight.eot');
src: url('http://thegem-wptheme.loc/wp-content/themes/TheGem/fonts/montserrat-ultralight.eot?#iefix') 

Not sure if "thegem-wptheme.loc" is supposed to resolve or be replaced, but removing "http://thegem-wptheme.loc" fixes the issue.

In the child theme's custom css file (thegem-child/css/custom.css) the URL for Montserrat Ultralight starts with http://thegem-wptheme.loc/, which isn't an active URL.

thegem-wptheme.loc’s server DNS address could not be found.

DNS_PROBE_FINISHED_NXDOMAIN

@font-face {
font-family: 'Montserrat UltraLight';
src: url('http://thegem-wptheme.loc/wp-content/themes/TheGem/fonts/montserrat-ultralight.eot');
src: url('http://thegem-wptheme.loc/wp-content/themes/TheGem/fonts/montserrat-ultralight.eot?#iefix') format('embedded-opentype'),
url('http://thegem-wptheme.loc/wp-content/themes/TheGem/fonts/montserrat-ultralight.woff') format('woff'),
url('http://thegem-wptheme.loc/wp-content/themes/TheGem/fonts/montserrat-ultralight.ttf') format('truetype'),
url('http://thegem-wptheme.loc/wp-content/themes/TheGem/fonts/montserrat-ultralight.svg#montserratultra_light') format('svg');
font-weight: normal;
font-style: normal;
}

I already fixed it, I was just letting you know, in case others had the same problem.