Please use the </> when posting code

{
    module: 'MMM-Remote-Control'
    // uncomment the following line to show the URL of the remote control on the mirror
    // , position: 'bottom_left'
    // you can hide this module afterwards from the remote control itself
    config: {
        customCommand: {},  // Optional, See "Using Custom Commands" below
        customMenu: "custom_menu.json", // Optional, See "Custom Menu Items" below
        showModuleApiMenu: true, // Optional, Enable the Module Controls menu
        apiKey: "",         // Optional, See API/README.md for details
    }
},

My guess is that your problem is within point 3.

(3) For security reasons, the MagicMirror (and therefore the Remote Control) is not reachable externally. To change this, configure address, and ipWhitelist in your config.js (see these lines in the sample config). For
example change address to 0.0.0.0 and add two allowed devices with IP-Adresses 192.168.0.42 and 192.168.0.50:

address : ‘0.0.0.0’,
port: 8080,
ipWhitelist: [“127.0.0.1”, “::ffff:127.0.0.1”, “::1”, “::ffff:192.168.0.42”, “::ffff:192.168.0.50”],"

You can also add multiple devices in an IP range (e.g. all devices with 192.168.0.X):

ipWhitelist: ["127.0.0.1", "::ffff:127.0.0.1", "::1", "::ffff:192.168.0.1/120", "192.168.0.1/24"],