Spring-Cloud Hystrix (fallback method wasn't found)

I think the exception is clearly telling you the issue. The method:

public String breaker(EnrollCommand command) {
    System.out.println("HYSTRIX EXECUTADO");
    return "Hystrix is Ok";
}

Does not exist. (Notice the argument in the signature)

When you define a fallback method with that annotation the fallback method must match the same parameters of the method where you define the Hystrix Command.