With the upgrade to WordPress 4.7.1, some non-image files fail to upload on certain server setups. This will be fixed in 4.7.3, see the Trac ticket.
In the meantime, this plugin is a workaround that disables the recently introduced strict MIME check to restore the upload functionality.
Don’t forget to remove the plugin once WordPress 4.7.3 is available!
This plugin is available for download for your site.