I'm not sure why I face an "Internal Server Error" when I send an POST Request with Power Automate, but if I send the same request with Postman it works just fine. As you can see the flow tried 4 times until it stopped. I call the same REST API with Postman and it works without problems. The Authorization is by the way Basic with Username and Password.

This is the response from Postman when I send the POST request:

{
"executionTime": 3360,
"hints": [
    {
        "id": "STRING",
        "name": "STRING",
        "type": "GROUP_HINT",
        "locations": [
            {
                "tokens": [
                    {
                        "start": 33,
                        "end": 41
                    },
                    {
                        "start": 61,
                        "end": 66
                    }
                ],
                "score": 1.0,
                "distance": 0,
                "groupValue": {
                    "left": "STRING",
                    "right": "STRING"
                }
            }
        ],
        "groupElement": [
            "MATCHED GROUPS"
        ],
        "range": 20
    }
],
"businessCases": [
    {
        "businessCaseId": "ee05f8f9-e18d-4bf7-b7db-4c8bc800615a",
        "name": "STRING",
        "score": 0.53,
        "hintCount": 1596,
        "originCount": 241,
        "matchedHints": [
            "MATCHED GROUPS"
        ],
        "matchedBoostedHints": [
            "MATCHED GROUPS"
        ],
        "origins": [],
        "matchedOrigins": [
            "MATCHED GROUPS"
        ],
        "matchedBoostedOrigins": [
            "MATCHED GROUPS"
        ],
        "unmatchedOrigins": []
    }
],
"questions": [],
"extractedValues": []

}

The REST API should analyse the text in the POST request and return any matched groups through sentiment analysis.