Error when building a .tmx file with mgcb editor

Hello, I’m trying to build the sample tiled map https://github.com/craftworkgames/MonoGame.Extended-samples/tree/2d1c244306a385ac19dd76b3b71d2fb838ec0f60/src/Demos/Tutorials/Content/TiledMaps within the mgcb editor, but I always get this error


however i made sure the Monogame.Extended.Content.Pipeline.dll is referenced. Could anyone help me with this please ?