Stolen packages - how to encourage Police to take action?

Hi,

A few weeks ago, a package addressed to me was stolen from the apartment lobby (together with packages addressed to a few other residents).

Since it was quite expensive (~600€) and the entire building has pretty good CCTV system, I reported it to the police, hoping that it will be slam dunk case for them.

Unfortunately, they declined to further investigate the case. They didn't even bothered to look at CCTV footage.

In meantime, the thefts continue.

It is not a monetary issue for me (seller refunded me), but by not prosecuting this we are enabling serial thief and putting other people at risk.

What are my chances and the best approach to force police and prosecution office to take action and actually try to solve the issue?