GetThumbnail with urn got from Data Management API returned 404

Question

I am trying to get the thumbnail from a file uploaded to BIM 360, with these returned from Data Management API folderContent call:

        "thumbnails": {
          "data": {
            "type": "thumbnails",
            "id": "dXJuOmFkc2sud2lwcHJvZDpmcy5maWxlOnZmLjhzdDB2Sk9tUkxPNEF3cVR5cWFCSFE_dmVyc2lvbj0x"
          },
          "meta": {
            "link": {
              "href": "https://developer.api.autodesk.com/modelderivative/v2/designdata/dXJuOmFkc2sud2lwcHJvZDpmcy5maWxlOnZmLjhzdDB2Sk9tUkxPNEF3cVR5cWFCSFE_dmVyc2lvbj0x/thumbnail?scopes=b360project.1cf212f9-8f18-426f-bde3-1528880626fb,O2tenant.25172440"
            }
          }
        },

Q1: the thumbnails.data.id seems not a urn that can be used with GetThumbnail (I am using forge-apis. What is this data id? It seems a base64 encoded usual urn. If I decode it and use it to GET the thumbnail I got 400: statusBody: { diagnostic: 'The requested thumbnail urn is invalid.' }}

Q2: GET the thumbnails.meta.link.href gives 404. Is this expected? How can I get a thumbnail for the item?

{
  status: 404,
  statusText: 'Not Found',
  headers: {
    date: 'Tue, 31 Oct 2023 21:23:23 GMT',
    'strict-transport-security': 'max-age=31536000; includeSubDomains',
    'x-ads-app-identifier': 'platform-viewing-2023.10.01.417.dca5d79ee-production',
    'x-ads-duration': '46 ms',
    'x-ads-startup-time': 'Fri Oct 27 08:21:54 UTC 2023',
    'x-ads-troubleshooting': 'The graph node specified by the urn/id was not found',
    'content-length': '0',
    connection: 'Close'
  },

Answer 1

Don't decode thumbnails.data.id, use it as it is.

Here's an example of thumbnail implementation: https://github.com/libvarun/oss-gallery/blob/main/public/js/main.js#L41