You can download the Windows Device Recovery Tool on your PC and use it to fix software problems on your phone. It'll install the latest version of Windows approved for your phone and remove everything else, including your apps, games, texts, call history, music, and photos. Before you use this tool, see if restarting or resetting your phone fixes the problem.
Looking for help with HoloLens? Check out Restart, reset, or recover your HoloLens