From AWS's documentation
A system status check failure indicates a problem with the AWS systems that your instance runs on. When a problem with an underlying host impacts your production, you can stop and start your instance to migrate from the current underlying host.
Resolution and more information at https://aws.amazon.com/premiumsupport/knowledge-center/ec2-windows-system-status-check-fail/#:~:text=A%20system%20status%20check%20failure%20indicates%20a%20problem%20with%20the,from%20the%20current%20underlying%20host.
Please click "Accept" if this Answer works for you
I would check the system log under "Actions -> Monitoring and troubleshooting -> Get system log" to see if there was a clue as to why it is not booting up. If you find something actionable, stop the instance, detach the boot volume, attach the volume to a running instance, mount in on the OS, and fix the issue. Then mount it back on the original instance and start. You may also try to connect to the instance of the EC2 Serial Console and troubleshoot from there. If all else fails, create a new instance using the snapshot you created before the upgrade.
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