This problem happens because IIS does not find the actual location of woff2 file mime types. Set URL of font-face properly, also keep font-family as glyphicons-halflings-regular in your CSS file as shown below.
@font-face {
font-family: 'glyphicons-halflings-regular';
src: url('../../../fonts/glyphicons-halflings-regular.woff2') format('woff2');}