kellyfettes-
If you look closely (under the busbar), you should see a circuit breaker. One end is attached to the busbar, and the other to the ring terminal that feeds the converter. I suspect you need to replace that circuit breaker.
If the circuit breaker has a very small black button on it, it is a manual-reset breaker. Try pressing the button to see if the breaker resets and you get 12V on the converter terminal. If no joy, then you need to replace the breaker. Amazon link
here.
If the circuit breaker does not have a small button on it, it is probably a self-resetting type, and must be replaced. Amazon link
here.