Uncaught TypeError: Cannot read properties of undefined (reading 'loadNFTMarker')

This error typically occurs when the `loadNFTMarker` function is called on an undefined object. There are a few potential reasons why this error might be happening:

1. The `aframe-ar-nft.js` library is not properly loaded: Make sure that you have included the `aframe-ar-nft.js` library in your HTML file and that it is loaded before you attempt to call the `loadNFTMarker` function.

2. The `a-scene` element or the AR component is not available: Verify that you have an `a-scene` element in your HTML file and that it has the `arjs` component attached to it. You can check this by inspecting the DOM in your browser's developer tools.

3. The `a-scene` component is not fully initialized: If you are calling the `loadNFTMarker` function immediately after adding the NFT marker, it's possible that the AR component hasn't finished initializing yet. You can try adding a small delay before calling `loadNFTMarker` to ensure that the AR component is fully initialized before the function is called.

Here's an example of how you can add a delay before calling `loadNFTMarker`:

function addNFTMarker() {
  // ... create and add the NFT marker ...

  // Add a small delay before calling loadNFTMarker
  setTimeout(function() {
    var arComponent = document.querySelector("a-scene").components.arjs;
    arComponent.loadNFTMarker(markerId);
  }, 100);
}

By using `setTimeout`, we delay the execution of `loadNFTMarker` by 100 milliseconds, giving enough time for the AR component to initialize.

Make sure to double-check your code and verify that all necessary components and libraries are properly loaded and initialized before attempting to call `loadNFTMarker`.