500 error with Samanage API Powershell


I was playing around with the API, but i cant figure out how to make it work.

I successfuly authenticated and i can make GET requests to gather an incident for example.

But when i want to update or create an incident (using PUT or POST), i constantly have a 500 error.

$URI = "https://apieu.samanage.com/incidents/10498330"
$Body = @"

    "incident" : {
        "name": "bonjour",
        "description": "ceci est un test",
        "category": {
            "name": "Bureautique"
        "requester": {
            "email": "xxxxxxxxxxx"

$Request2 = Invoke-WebRequest -URI $URI -Method PUT -Body $Body -Headers $Headers  

The body is correctly formated to json.

Thanks for your help!