AWS BigIP VE SSH root login failure

I have created an SSH key via the AWS console, downloaded it, set the permissions right and used it to launch the appliance with. I thought I was going crazy and later on once I've terminated and relaunched a couple of appliances, I selected a different SSH key to launch the appliance with, an SSH key that I've used to spin up other instances, to make sure that it wasn't something with the key. But unfortunately, the same problem, i can connect to the appliance, it starts the key exchange and then the server closes the connection.

I am supposed to SSH in as root right? I've also tried ec2-user, but that asks for a password that I do not have.

Is there a way to log in to the web interface, a default admin password, that I can use?