They told me that it takes 2-4 weeks as well, but my ceremony was on August 26th and I am still waiting (over 7 weeks). I called IRCC many times and they confirmed there is no issues on my side and it is in queue for printing, so I have no idea what is going on there.
That being said, it is not a normal situation I am in and most people on the forum report receiving their certificates in 2-3 weeks.