I am having a similar problem.
I am trying to extend the ccsave payment method with a new verison that only has a change in the isAvailable() method.
I’ve done that and all and my Payment method shows up in the front end and the backend..
However during the one page checkout, when I reach the payment method step and fill in test cc data (that validates when i use the ccsave method) when I click continue nothing happens.
I am not sure what I am doing wrong.