WASHINGTON — TikTok was not available for users in the U.S. on Saturday as a ban on the popular social media platform officially went into effect. TikTok greeted users opening the app Saturday night with the message, "Sorry, TikTok isn't available right now.""A law banning TikTok has been enacted in the U.S.," the message continued. "Unfortunately, that means you can't use TikTok for now. We are fortunate that President Trump has indicated that he will work with us on a solution to reinstate Tik...