Have you applied for Chief Security Officer, his deputy, or as an ordinary security guard? I've never seen anyone who wasn't from the "3rd World" as an ordinary security guard as the pay is poor and the hours very long. I know some security guards that legitimately never get off the ship their entore contract.
As for the application process, it all depends on your experience, and when they need someone. A lot of the Chief's, deputies and even ordinary security have military experience. I would also imagine someone from Germany would have the extra problem of RCCL wondering why someone from a developed country would want the job of an ordinary security guard?