Hi @tdct_1991 , welcome to Microsoft Q&A forum.
This issue mostly looks like due to providing proper access to roles. I was able to post the request using the Postman. There are 3 things we need to set up as mentioned in the article. Could you please confirm if you have done these:
- Register a confidential client application in Azure Active Directory
- Configure Azure RBAC for FHIR
- Obtaining the access token
Please let me know if this helps or we can discuss further.
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If answer helps, please mark it 'Accept Answer'