Started getting 400 Bad Request attempting to refresh OAuth 2.0 Tokens

[ptbonterra]

We have Java code that would refresh OAuth 2.0 Code Flow Tokens based on this guide:

https://opensource.adobe.com/acrobat-sign/developer_guide/helloworld.html#refresh-token-request

After having this running fine, I did make changes to our Java code, and noticed that I can no longer refresh tokens.  

I figured my changes broke our code.  However, I stepped back and created a pure Postman Request and am getting a 400 Bad Request in Postman:

Notes:

1. The POST Url is the Shard that came back as the api_access_point, to which we appended /oauth/v2/refresh
2. I double checked our Client ID and Client Secret, they are correct.  Also this is a certified app.
3. The Test Refresh Token was obtained today

Are there issues with refreshing tokens on Adobe's side at the moment?  Are others able to refresh tokens?