Hi @dwedwick,
We created a post for this, and sent out a few emails regarding the change. Perhaps we missed your email address.
Update information can be found here: API label/rate endpoint deprecation on 2017-09-30.
You can see in the docs link given in the response, the params for those endpoints below http://docs.devapiverson.apiary.io/#reference/v2
Please now use the following endpoints for USPS via Endicia.
/shipment/:shipment_id/label/endicia [POST]/shipment/:shipment_id/rate/endicia [GET]
Let us know if you have any other questions.