EC2 Instance Connect - Rocky 8

First time trying the Rocky 8 image available on EC2 through the marketplace.

I’m able to SSH in with the supplied key-pair as the rocky user, but not able to connect using EC2 Instance Connect, is this supported?

EC2 Instance Connect just says “Error establishing SSH connection to your instance. Try again later.”

Looking at /var/log/secure (the only thing logged to), it just says "Connection closed by authenticating user rocky port [preauth]

Should this work? I’m guessing the ssh server might need a configuration tweak?