How to connect aws instance with aws cli?

I don't have ssh key but I have access to aws portal and console where the ec2 machine is there.

I tried using the steps in this link to connect ec2 instance.

Method 1:

using only instance-id and mssh

mssh i-038317982dc6a7c64 Unable to init server: Could not connect: Connection refused (mssh:2876): Gtk-WARNING **: 14:03:20.071: cannot open display: 

Method 2: To generate a new ssh key and push that to ec2 instance.

aws ec2-instance-connect send-ssh-public-key --instance-id i-038317982dc6a7c64 --availability-zone us-east-1b --instance-os-user ec2-user --ssh-public-key file://my_key.pub An error occurred (EC2InstanceNotFoundException) when calling the SendSSHPublicKey operation: Instance not found. 

But that machine is there.

So I tried by providing region also.

aws ec2-instance-connect send-ssh-public-key --instance-id i-038317982dc6a7c64 --availability-zone us-east-1b --region us-east-1 --instance-os-user ec2-user --ssh-public-key file://my_key.pub { "RequestId": "9ecd1748-1ef3-4b7b-b1a5-5ae4370df452", "Success": true } 

Then, I tried connecting with ssh.

But with dns name or ip address, I am getting permission denied only.

ssh -o "IdentitiesOnly=yes" -i my_key [email protected] The authenticity of host '54.174.85.61 (54.174.85.61)' can't be established. ECDSA key fingerprint is SHA256:7hTrm5wLeicqFVbNG9MW7HDEqUZQDi/H/OzJ3AwL0zU. Are you sure you want to continue connecting (yes/no/[fingerprint])? yes Warning: Permanently added '54.174.85.61' (ECDSA) to the list of known hosts. [email protected]: Permission denied (publickey,gssapi-keyex,gssapi-with-mic). ssh -o "IdentitiesOnly=yes" -i my_key [email protected] The authenticity of host 'ec2-54-174-85-61.compute-1.amazonaws.com (54.174.85.61)' can't be established. ECDSA key fingerprint is SHA256:7hTrm5wLeicqFVbNG9MW7HDEqUZQDi/H/OzJ3AwL0zU. Are you sure you want to continue connecting (yes/no/[fingerprint])? yes Warning: Permanently added 'ec2-54-174-85-61.compute-1.amazonaws.com' (ECDSA) to the list of known hosts. [email protected]: Permission denied (publickey,gssapi-keyex,gssapi-with-mic). 

Please suggest what are the options available to connect aws linux 2 machine with aws credentials configured in the console and having instanceid/machine dns name or ip address