How to get an Access Token from a Refresh token from within B4A

Greg,

I had a look at the documentation and it appears the command I need is this one:

curl https://api.dropbox.com/oauth2/token \
    -d grant_type=refresh_token \
    -d refresh_token=<REFRESH_TOKEN> \
    -d client_id=<APP_KEY> \
    -d client_secret=<APP_SECRET>

I have tried to apply this in my B4A code as follows:

Dim data As Map
	data.Initialize
	data.Put("grant_type", "refresh_token")
	data.Put("refresh_token", "REFRESH_TOKEN")
	data.Put("client_id", "APP_KEY")
	data.Put("client_secret", "APP_SECRET")
	
	Dim j As HttpJob
	j.Initialize("", Me)
	j.PostString("https://api.dropbox.com/oauth2/token",data.As(JSON).ToString)
	j.GetRequest.SetContentType("application/json")
	Wait For (j) JobDone(j As HttpJob)
	If j.Success Then
		Log(j.GetString)
	Else
		Log(j.ErrorMessage)
	End If
	
	j.Release

But I get this error:

ResponseError. Reason: , Response: {"error": "invalid_request", "error_description": "The request parameters do not match any of the supported authorization flows. Please refer to the API documentation for the correct parameters."}

While I realize you may not be familiar with this language, is there anything glaringly wrong from what you see?

Thanks Brad