Hi!
It appears you are trying to use the shipments API with a v3 account. This is not recommended nor supported. Note: We are in the process of deprecating use of these endpoints with with v3 accounts to prevent issues like this.
Have you seen the v3 Orders API? We have a link listed in the Ordoro Docs, but you can visit directly https://devapiverson.docs.apiary.io/.
If you are using Ordoro 3, you must use the v3 Orders API to perform any functions pertaining to orders, including updating tracking information.
You should POST to /shipping_info.
See this previous forum question about the same thing. API to add tracking information to order
Hope this helps!