HTTP 400 on Yammer image with "InvalidOrMissingClaims" reason

Question

Hi,

We have integrated Yammer feed into our client app and we are now trying to display images in there.

As attachement URLs are protected, we are trying to implement a proxy to load files from Yammer and deal with the Yammer authorization token.

The authorization token seems to be properly handled, as we don't face HTTP 401 anymore, however we moved to another issue: the request now returns a HTTP 400 with an error payload:

curl \
--location 'https://www.yammer.com/api/v1/uploaded_files/[REDACTED]/version/[REDACTED]/thumbnail' \
--header 'Authorization: Bearer [YAMMER_TOKEN]' \

and the result:

{
   "reason": "InvalidOrMissingClaims"
}

We were not able to find any documentation nor StackOverflow post about this issue.

Any help would be greatly appreciated!