Php 带有Lumen的JWT认证API在登录时始终返回401 unauthorized

我遵循了教程：

public function login(Request $request)
        {
            //validate incoming request
            $this->validate($request, [
                'email' => 'required|string',
                'password' => 'required|string',
            ]);

            $credentials = $request->only(['email', 'password']);
            var_dump($credentials);
            echo Auth::attempt($credentials);

            if (! $token = Auth::attempt($credentials)) {
                return response()->json(['message' => 'Unauthorized'], 401);
            }

            return $this->respondWithToken($token);
        }

我的问题是

带有Lumen的JWT认证API在登录时始终返回401 unauthorized