Unable to reach AWS EC2 node

• Please check and review your security groups on each instance for inbound and outbound rules.
• If between subnets, ensure the NACLs allow connectivity.
• If in different VPCs, ensure you have the correct routing inplace between them.

If the problem is network connectivity then the solution will be one of the items in @Gary's answer.

Also, if you're connecting between EC2s in the same VPC (or in peered VPCs) make sure it's the private IP you're using.

If a connection can be established from the source EC2 to the target EC2 then look at the method of authentication.

For SSH to work the source EC2 is going to need to present the private key that matches the public key for that user on the target EC2.

For telnet to work, the telnet-server package needs to be installed on the target EC2, and it almost certainly won't be by default - see https://repost.aws/questions/QUTZ-MGNKRSCG3KOeH2qqyFg/how-do-you-create-a-instance-that-allows-telnet#AN4MDvMHYbSDeIIsEfRZ_H0Q