How to use WMS offline

How to use CesiumWebMapServiceRasterOverlay offline

You use a WMS offline just as you’re doing. The error you circled is a result of the tileset that you’ve attached the raster overlay to. It looks like you’ve configured it to connect to Cesium World Terrain on Cesium ion. You’ll need an offline source of terrain (geometry) in addition to the offline overlay.

thank you so much