Data-form to Raw Json Format

Data-form to Raw Json Format

I'm trying to covert an data-form entry into a Raw Json Format in a POST API call on Postman and it's not working well.

The API Instruction for data-form input: Website


And it's works well when I use that data-form configuration for my API:

But the problem is that I must convert that data-form arguments input into a Raw Json format and it's not working.

The way that I'm trying to use as Raw Json format (Content-Type already as application/json) is:

{
    "arguments": {
        "Hi_eid": "*******-****-****-****-e2e1bf4c52e9"
    } 
}

The wierd thing is that the status says thats working "200" but the response says that the data was invalid as Invalid collection string. And I don't know what I'm doing wrong.

May someone help me with that issue?​