This was posted a few hours ago on their Twitter @play_pso2. Hopefully they fix the issue quickly, cuz I'm one of those players that can't play the game.
Hello, Arks. We want to reassure you that the #PSO2NA team is paying close attention to all your comments from social media and across the web. We are working closely with Microsoft to reach a solution to the issues you have experienced during the game’s launch on Windows 10. We deeply apologize for the inconvenience and the negative experience some of you have had when trying to download and install the game. Please know that we are working hard to solve these problems and that we appreciate your patience. We will release additional announcements and notices soon. Please stay tuned to our official website and social media accounts for further updates.