A few months ago, Satya Nadella, the chief executive of Microsoft, hosted a technology summit meeting at the company's headquarters near Seattle with some of China's most powerful political leaders. He smiled for a photo while flanked by Xi Jinping, the country's president, and Lu Wei, its Internet czar. On Tuesday, though, that harmony faded, as one of China's regulators said it would demand answers to new questions about Microsoft's business practices there. The announcement, related to electronic data that the government collected in an antitrust inquiry, shows how a ...