Dropbox API v2, gateway credential error

I have to connect the Dropbox cloud straight to Power BI cloud (service).

Using the code from this post, I can load data to Power BI Desktop (thanks to ImkeF), but I get credential error when trying to refresh the data on Power BI Service.

The code below works great on Power BI Desktop, but I need to be able to refresh data from inside Power BI Service.

Do I need to use another code?
Any tip on how to get correct credentials on gateway?

let
token = "<<FillInYourTokenHere>>",
folder = null, // replace null with folder name if you want to use it
    data = [    path= if folder = null then "" else folder,
                recursive=false,
                include_media_info=false,
                include_deleted=false,
                include_has_explicit_shared_members=false
],
    header = [  #"Authorization"="Bearer "&token,
                #"Content-Type"= "application/json"],
    response = Web.Contents("https://api.dropboxapi.com/2/files/list_folder",[Content=Json.FromValue(data),Headers=header]),
    out = Json.Document(response,1252),
    entries = out[entries],
    ToTable = Table.FromList(entries, Splitter.SplitByNothing(), null, null, ExtraValues.Error),
    ExpandProperties = Table.ExpandRecordColumn(ToTable, "Column1", {".tag", "name", "path_lower", "path_display", "id", "client_modified", "server_modified", "rev", "size", "content_hash"}, {".tag", "name", "path_lower", "path_display", "id", "client_modified", "server_modified", "rev", "size", "content_hash"}),
    RetrieveContent = Table.AddColumn(ExpandProperties, "File", each Web.Contents("https://content.dropboxapi.com/2/files/download",[
    Headers=[#"Dropbox-API-Arg"="{""path"":"""&[path_display]&"""}", #"Authorization" = header[Authorization]]]))

in
RetrieveContent