Accessing Drive thumbnailLink with gapi.client.request gives 404 - reactjs

Question

I'm currently working on a React app that should load a set of (non-public) files from a user's Google Drive and display thumbnails using the CSS background-image: url(...) property. I can load all of the file metadata using the Gapi Files:get method, and an OAuth token is set ahead of time using gapi.client.setToken. I'm hoping to load the thumbnail as follows:
function CollectionArtifact(props){
const [thumbnail, setThumbnail] = useState(null);
async function loadThumbnail(){
try {
const res = await window.gapi.client.request(props.artifact.thumbnailLink);
const data = await res.blob();
const localURL = URL.createObjectUrl(data);
setThumbnail(localURL);
catch(e){ console.log('Failed to load thumbnail', e); }
}
useEffect(() => {
if(props.apisLoaded){
loadThumbnail();
}
}, [props.apisLoaded]);
return (
...
<div style={{backgroundImage: `url(${thumbnail})`}}>
...
</div>
...
);
}
The client is initialized in a wrapper component like so:
window.gapi.load('client:auth2', () => {
window.gapi.client.init({
apiKey: developerKey,
clientId: clientId,
scope: 'https://www.googleapis.com/auth/drive'
}).then(() => {
window.gapi.client.load('drive', 'v3', () => {
if(props.onGapisLoad) props.onGapisLoad();
setInitialized(true);
});
});
});
However, the window.gapi.client.request call gives Failed to load resource: the server responded with a status of 404, and the URL that's actually giving this error is the proxy request https://docs.google.com/static/proxy.html?usegapi=1&.... Using fetch also doesn't work, as it gives a CORS error. Meanwhile, if I try to access the thumbnailLink in the browser while signed in to the correct Google account (and no other accounts), I can see the image without a problem.
What would be the proper way to load thumbnails through an authorized request? I've seen other answers that recommend generating a PDF and using it to create a public thumbnail, but I'd like to avoid creating extra files in the user's drive or making file data publicly accessible. And since the image can be loaded directly from the browser, I would assume there's a way to access it with an authorized client.