FuelPHP routing is case sensitive by default, TOKEN !== token.
You can make routing case insensitive in your application config file, in the routing section. See fuel/core/config/config.php if you don't have this section in your app config, and copy it over before you change it.
This is an application wide setting, so if you only want this for specific routes, you'll have to add a route with a regex for it so it matches any case.