So how did you resolve this? Did you need to get a new refresh token (reauthorize the app to get a new refresh token)

I am experiencing a similar issue but with Amazon Warehousing and Distribution API, I have been using other APIs without issue for some time. In general we are using the Python-Amazon-SP-API Library.

1. Update the Developer profile for new role like AWD and wait for approval.
2. Edit the apps to have the new role in my case AWD
3. Get new resfresh token buy authorizing the app.

I am still getting the 'code':'Unauthorized' message.