Even i am receiving the same.

I have performed following steps:
1. created SP on Azure.
2. Granted contributor role on azure resource where DBx workspace is created.
3. Gerated token using, az account get-access-token --resource 2ff814a6-3304-4ab8-85cb-cd0e6f879c1d.
4. Used this token as bearer token for calling DBx create token api.
5. But in the response i get status code as 200 and html code.

In my scenario i am calling a powershell inline script in azure ci pipeline. Also i tried to replicated the same process via postman, i revceive the same error.

Note: If i use all the above information and execute the command locally on power shell, it works fine and returns me token.