It appears to be an issue like this.
After entering webXR, try add camera to the pipeline
scene.createDefaultXRExperienceAsync({
floorMeshes: [scene.getMeshByName("Sols")]
}).then((xr) => {
xr.baseExperience.sessionManager.onXRFrameObservable.addOnce(() => {
defaultPipeline.addCamera(xr.baseExperience.camera)
});
});