Windows 10 includes Windows Security, which provides the latest antivirus protection. Your device will be actively protected from the moment you start Windows 10. Windows Security continually scans for malware (malicious software), viruses, and security threats. In addition to this real-time protection, updates are downloaded automatically to help keep your device safe and protect it from threats.
If Windows Security is crashing or not opening, you can reset and/or re-register the Windows Security app to hopefully fix it.
This tutorial will show you how to reset and re-register the Windows Security app for your account in Windows 10.