All I can do is to compare the requests that get made with a page like https://webhook.site/ and there it looks like the same data does get send. So sadly no idea what is going on.
So what you can try (in that order):
Upgrade to the latest n8n version
Set the environment variable N8N_USE_DEPRECATED_REQUEST_LIB=true
Debug yourself or create something reproducible that you can share
Thanks @jan. That helped me to the answer. As the payload has not changed I guessed the endpoint may have changed and it has. For anyone else the new matterport end point to use is https://api.matterport.com/api/models/graph?