I did a quick test: when adding glyphicon-<iconname> (e. g. glyphicon-asterisk), the glyphicon is displayed. Note that you do not need to add “glpyhicon glyphicon-asterisk”.
I've had this issue before, it could be that somewhere in your css you're overwriting the standard font-family where the glyphicons are stored.
You could take a look at that, if for example you have a button-scss property where you overwrite font-family (maybe with !important) it could mess up the included icons