Tried adding new map provider, running into issues.

Topics: Bugs, Help
Feb 8 at 2:37 PM
I tried adding a new map provider (GeoPortail, see below)
And it seems to be working for the most part, except that sometimes when i zoom in it does not grab the imagery. I have to switch map type and switch back before it starts grabbing again.
I am not sure if I did something wrong.
  string MakeTileImageUrl(GPoint pos, int zoom, string language)

     return string.Format(UrlFormat, zoom, pos.Y, pos.X);

  static readonly string UrlFormat = "{0}&TileCol={2}&TileRow={1}";