What could be the cause of the failed connection?
The security group does not allow inbound traffic on port 22.
The network ACL does not allow outbound traffic on port 80.
The security group does not allow outbound traffic on port 3389.
The network ACL does not allow inbound traffic on port 443.
Explanations:
The security group needs to allow inbound traffic on port 22 for SSH access. If the security group doesn’t permit inbound traffic on port 22, the SysOps administrator won’t be able to connect to the instance.
The network ACL allowing or blocking outbound traffic on port 80 has no impact on SSH connectivity (port 22). Port 80 is for HTTP, which is unrelated to the SSH issue.
The security group allowing or blocking outbound traffic on port 3389 is irrelevant to SSH connectivity (port 22). Port 3389 is for RDP, which is unrelated to the SSH issue.
The network ACL blocking inbound traffic on port 443 (HTTPS) has no impact on SSH connectivity (port 22). Port 443 is unrelated to SSH access, which uses port 22.
My best guess is:
The security group does not allow inbound traffic on port 22.