cesium load WMTS, tile map offset

var provider = new Cesium.WebMapTileServiceImageryProvider({
    url: 'xxx.xx.xxx',
    layer: 'RESPL_2018',
    style: 'default',
    format: 'image/png',
    tileMatrixSetID: 'xxx',
    tilingScheme: new Cesium.WebMercatorTilingScheme(),
});

This is how the map is loaded.I successfully loaded a map,but the latitude of the loaded map is offset by + 50 degrees. Is there any way to reset the starting point of the WMTS loading!