"No route to host" error suggests that there could be some network issue on your instance or that you are not connecting to correct address / host.
For network issue, check if your instance is passing all its system status checks. If some of them are failed, follow this AWS documentation:
You can share with me your instance console logs, they are available in AWS EC2 console:
As for the second reason, you have mentioned that this has happened after reboot.
Was that reboot or stop and start operation?
If stop and start, your IP address has changed if you have not used Elastic IP. This would explain "No route to host" - you simply do not connect to your instance.
Check your current IP and try to connect to it:
If this was the case, I would recommend using Elastic IP - this is static IP address that does not change upon stop and start operation. It is also free of charge if your instance is running:
Please note, when you assign Elastic IP to your instance, its IP will change. You cannot convert non-Elastic IP to Elastic one.
I hope that this will help you, if not feel free to reach out to me.
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