You still receiving same exact error or a different one?

If the same error try to run it this way:

curl --location 'https://<workspace_url>/api/2.0/unity-catalog/temporary-table-credentials' \
--header 'Content-Type: application/json' \
--header 'Authorization: Bearer ***********' \
--data '{
"table_id": "xxxx-c4b4-4827-a834-xxxxxxx",
"operation": "READ"
}'