I have the PubSub in correct order in application.ex but it still throws an error

application.ex

children = [
      # Start the Telemetry supervisor
      Pxf.Web.Telemetry,
      # Start the PubSub system
      {Phoenix.PubSub, name: Pxf.PubSub},
      # Start the Endpoint (http/https)
      Pxf.Web.Endpoint,
      # Start a worker by calling: Pxf.Worker.start_link(arg)
      # {Pxf.Worker, arg}
      Pxf.Scheduler,
      # web server plug
      {Plug.Cowboy, scheme: :http, plug: Pxf.Router, options: [port: 8000]}
]

Error

Last message: {Phoenix.Channel, %{}, {#PID<0.1038.0>, #Reference<0.2815987139.1106509825.214751>}, %Phoenix.Socket{assigns: %{}, channel: Phoenix.LiveReloader.Channel, channel_pid: nil, endpoint: Pxf.Web.Endpoint, handler: Phoenix.LiveReloader.Socket, id: nil, joined: false, join_ref: "103", private: %{}, pubsub_server: Pxf.PubSub, ref: nil, serializer: Phoenix.Socket.V2.JSONSerializer, topic: "phoenix:live_reload", transport: :websocket, transport_pid: #PID<0.1038.0>}}
State: #Reference<0.2815987139.1106509825.214753>
[error] an exception was raised:
    ** (ArgumentError) unknown registry: Pxf.PubSub
        (elixir 1.14.2) lib/registry.ex:1373: Registry.info!/1
        (elixir 1.14.2) lib/registry.ex:989: Registry.register/3
        (phoenix_pubsub 2.1.1) lib/phoenix/pubsub.ex:121: Phoenix.PubSub.subscribe/3
        (phoenix 1.6.15) lib/phoenix/channel/server.ex:419: Phoenix.Channel.Server.init_join/3
        (phoenix 1.6.15) lib/phoenix/channel/server.ex:378: Phoenix.Channel.Server.channel_join/4
        (phoenix 1.6.15) lib/phoenix/channel/server.ex:298: Phoenix.Channel.Server.handle_info/2
        (stdlib 4.1.1) gen_server.erl:1123: :gen_server.try_dispatch/4
        (stdlib 4.1.1) gen_server.erl:1200: :gen_server.handle_msg/6
        (stdlib 4.1.1) proc_lib.erl:240: :proc_lib.init_p_do_apply/3