B4J Question Sumup API again

pJob.PostString("https://api.sumup.com/token", "grant_type=client_credentials&client_id=5wxxxx&client_secret=2105caxxxx")

'https://developer.sumup.com/docs/api/generate-a-token/
Public Sub TestSumupPostURL
    Dim Link As String = "https://api.sumup.com/token"
    
    Dim Data As Map = CreateMap("client_id" : "xxxx", "client_secret" : "xxxxx", "code" : "xxxxx", "grant_type" : "refresh_token", "refresh_token" : "xxxxx")
    Dim Parameters  As String = Data.As(JSON).ToString
    Log(Parameters)

    Wait For (SumupPostURL(Link, Parameters)) Complete (DataResult As String)
    Log(DataResult)
    
End Sub

Public Sub SumupPostURL(URL As String, Parameters As String) As ResumableSub
    Dim Result As String
    Dim j As HttpJob
    Try
        j.Initialize("", Me)
        j.PostString (URL, Parameters)
        j.GetRequest.SetContentType("application/json")
        j.GetRequest.SetHeader("Accept","application/json")
        Wait For (j) JobDone(j As HttpJob)
        If j.Success Then
            Result = j.GetString
        Else
            Log(j.ErrorMessage)
        End If
    Catch
        Log(LastException)
    End Try
    j.Release
    Return Result
End Sub

Public Sub SumupPostURL(URL As String, Parameters As String) As ResumableSub
    Dim Result As String
    Dim j As HttpJob
    Try
        j.Initialize("", Me)
        j.PostString (URL, Parameters)
        j.GetRequest.SetHeader("Accept","application/json")
'        j.GetRequest.SetContentType("application/json")
        j.GetRequest.SetContentType("text/plain")
        Wait For (j) JobDone(j As HttpJob)
        If j.Success Then
            Result = j.GetString
        Else
            Log(j.ErrorMessage)
        End If
    Catch
        Log(LastException)
    End Try
    j.Release
    Return Result
End Sub