Here's how you can Re-register and Reinstall Cortana in Windows 10
Microsoft added a digital assistant in Windows 10 called Cortana which can recognize your voice and do some things for you like giving you information or automating some tasks. With Windows 10 version 2004, Microsoft is rolling out a new Cortana version which is now separated from the Search. It also has a number of new features, and can be updated from the Microsoft Store. If Cortana is not working, then you can re-register its package and reinstall Cortana in Windows 10.