Laravel PUT returns 404 Error

I have a put request in my web.php file and this particular request returns a 404 error while the other put request works fine.

Fine below my routes in web.php with attention on the last line

<?php

/*
|--------------------------------------------------------------------------
| Web Routes
|--------------------------------------------------------------------------
|
| Here is where you can register web routes for your application. These
| routes are loaded by the RouteServiceProvider within a group which
| contains the "web" middleware group. Now create something great!
|
*/

Route::get('/', function () {
    return redirect('/login');
});

Auth::routes(['verify' => true]);

Route::post('/profile', 'PagesController@save_profile')->name('savep');
Route::post('/s-an', 'PagesController@s_an')->name('san');
Route::post('/en/process-f', 'PagesController@fProcess')->name('f.process');

Route::get('/dashboard', 'HomeController@index')->name('home');

Route::get('/en/upload-img', 'PagesController@img_upload')->name('img');
Route::get('/en/ct-n-app', 'PagesController@n_app')->name('app');
Route::get('/at-sets', 'PagesController@at_sets')->name('sets');
Route::get('/en/f', 'PagesController@f')->name('f');
Route::put('/app/{app}', 'PagesController@app')->name('app.d');

/** Admin Routes */
Route::resource('admin/application', 'AdminController');
Route::get('/en/view-apps', 'PagesController@aViewApps');
Route::post('/en/gene-is', 'PagesController@gene_is')->name('ad.is');
Route::post('/en/gene-tx', 'PagesController@gene_tx')->name('ad.tx');
Route::post('/en/gene-cy', 'PagesController@gene_cy')->name('ad.cy');
Route::post('/en/gene-mf', 'PagesController@gene_mf')->name('ad.mf');
/** Admin Routes */

//This PUT REQUEST RETURNS 404
Route::put('/en/f/{$f}', 'PagesController@updateFunding')->name('up.f');