REST calls returning “Incorrect data center requested”

So, I AM using the urls found in Setup > Company > Company URL > SUITETALK (SOAP AND REST WEB SERVICES).

I’m making only REST calls, not SOAP.  The response is XML as if I made a SOAP call which I didn’t.

I get this in our Sandbox environment.  I AM able to query the Development environment and get the proper JSON response.

I am using Postman to make these calls. I switch the environments the dropdown at the upper right. The Dev environment is using the corresponding URL found under Company URL on the dev site.

I’ve checked the setup in both environments and all seems to be fine.  I use the tokens/keys/secrets that correspond to the appropriate environment.

Does anyone have any idea what might be the problem or where to look for clues?

—–ERROR below—-