I found a work around
// Loads the given webmap
private async Task LoadWebMapAsync(string wmId)
{
try
{
_portal = await ArcGISPortal.CreateAsync();
var item = await ArcGISPortalItem.CreateAsync(_portal, wmId);
var webmap = await WebMap.FromPortalItemAsync(item);
var vm = await WebMapViewModel.LoadAsync(webmap, _portal);
foreach (var layer in vm.Map.Layers)
{
//Add each layer individually
Map.Layers.Add(layer);
}
}
catch (Exception ex)
{
var vmr = new ErrorMessagesClass();
vmr.ErrorMessages(ex.Message);
}
}