I dowlaod emscripten form here and installed,but the latest help document of UnReal said " In versions 4.9 and later, emscripten and python are included in the engine distribution. You can find them in Engine/Source/ThirdParty/HTML5/emsdk/, but no configuration or additional installation is required to deploy to HTML5. " but when I Uninstall the emscripten ,it still does not work well.