It wasn’t initially apparent to me but, setting configuration parameters in lms.env.json only indicates to the LMS that you want to use it as part of an Oauth authentication; you still have to setup Oauth itself. We’ll use the Django admin console for this. For the Python/Django uninitiated, Django apps like LMS and CMS come with a “back end” admin console where additional configuration parameters are available beyond what you’ll find in the four JSON files in /edx/app/edxapp/. Refer to this screen shot for the URL path and guidelines for creating an Oauth client.
Note: I’ve seen conflicting documentation regarding the proper port assignment for the Ecommerce module. Some suggest 8002 whereas others say it should be 18130. After some experimentation I’ve learned that either of these assignments will work, provided that you are consistent with your settings in /edx/app/edxapp/*.json and /edx/etc/ecommerce.yml and /etc/nginx/sites-enabled/ecommerce.