The 'create Upload Destination ForResource' operation on the SP API keeps returning 'Unauthorized'

The "Unauthorized" error you're encountering with the 'createUploadDestinationForResource' operation in the SP API suggests that there might be an issue with the permissions or authentication for this specific action. Even though other interfaces are working normally, this particular operation may require additional or different permissions.

To resolve this issue, you should consider the following steps:

1. Check the IAM permissions: Ensure that the IAM user or role you're using has the necessary permissions to perform the 'createUploadDestinationForResource' action. You may need to review and update the IAM policy attached to your user or role.

2. Verify API credentials: Make sure you're using the correct API credentials for this operation. Sometimes, different operations may require different levels of access or specific API keys.

3. Review API Gateway settings: If you're using API Gateway, check that the authorization settings for this specific resource and method are correctly configured.

4. Check for any service-specific requirements: Some AWS services may have additional authentication or authorization requirements for certain operations. Review the documentation for the SP API to see if there are any special considerations for this particular action.

5. Ensure consistency: If you've recently made changes to permissions or authentication settings, be aware that due to the eventual consistency model of AWS services, it may take some time for these changes to propagate across all regions and availability zones.

6. Examine error details: Try to obtain more detailed error information if possible. The exact error message or any additional error codes can provide more insight into the specific cause of the unauthorized access.

If the issue persists after checking these points, you may need to contact AWS Support for further assistance, as there could be a service-specific issue or a more complex configuration problem that requires deeper investigation.
Sources
Troubleshooting API request errors - Amazon Elastic Compute Cloud
CreateResource - Amazon API Gateway
Unauthorized running AppSync Query | AWS re:Post