WASHINGTON — TikTok stopped working in the United States late on Saturday and disappeared from Apple and Google app stores ahead of a law that takes effect Sunday requiring the shutdown of the app used by 170 million Americans. President-elect Donald Trump said earlier in the day he would “most likely” give TikTok a 90-day reprieve from the ban after he takes office on Monday, a promise TikTok cited in a notice posted to users on the app. TikTok, which is owned by China’s ByteDance, told users attempting to use the app around 10:45 p.m. ET (0345 GMT): “A law