Using TrackedEntity to reach satellite objects will result in a white screen

This is the part of my code about TrackedEntity:

document.addEventListener(“keydown”, function (event) {
if (event.key === “1”) {
changeTrackedEntity(“Satellite/B6-GPS_BIII-4_-chase11”);
} else if (event.key === “2”) {
changeTrackedEntity(“Satellite/B6-GPS_BIII-4_-chase5”);
} else if (event.key === “3”) {
changeTrackedEntity(“Satellite/B6-GPS_BIII-4_-chase7”);
}

After I added the code for the Earth’s rotation effect, the TrackedEntity function encountered an issue. Pressing the number key triggered TrackedEntity, which resulted in a white screen.This is the rotation function code:

class GlobeRotate {
constructor(viewer) {
this._viewer = viewer;
}

_icrf() {
    if (this._viewer.scene.mode !== Cesium.SceneMode.SCENE3D) {
        return ture;
    }
    // console.log(this._viewer.camera.position);
    let icrfToFixed = Cesium.Transforms.computeIcrfToFixedMatrix(this._viewer.clock.currentTime);
    if (icrfToFixed) {
        let camera = this._viewer.camera;
        let offset = Cesium.Cartesian3.clone(camera.position);
        let transform = Cesium.Matrix4.fromRotationTranslation(icrfToFixed);
 
        camera.lookAtTransform(transform, offset);
    }
}

_bindEvent() {
    this._viewer.clock.multiplier = 1;
    this._viewer.camera.lookAtTransform(Cesium.Matrix4.IDENTITY);
    this._viewer.scene.postUpdate.addEventListener(this._icrf, this);
}

_unbindEvent() {
    this._viewer.clock.multiplier = 1;
    this._viewer.camera.lookAtTransform(Cesium.Matrix4.IDENTITY);
    this._viewer.scene.postUpdate.removeEventListener(this._icrf, this);
}

start() {
    this._viewer.clock.shouldAnimate = true;
    this._unbindEvent();
    this._bindEvent();
    return this;
}

stop() {
    this._unbindEvent();
    return this;
}

}

Can you help me see where the problem is? Appreciate very much.