My package is delayed and the tracking is stuck on "sent to airline". Why?

Tomorrow it'll be a month since my package had been delivered to the airline. Ever since, there was no developments. Why is it so? I know that shipping to Poland might take a while, but I was lead to believe that it wouldn't take more than 3-4 weeks.
I've also heard that the tracking info might not be updated while the parcel is being shipped, but I think there would at least be an information that it's on its way?
My tracking number is: RB563878270CN.
I would greatly appreciate some help/advice.