Package accepted but no one picks it up? You must not make these mistakes under any circumstances. If you still haven't heard from your neighbor after more than two weeks, you can return the package to the sender.
If the recipient does not live in your home or neighborhood at all, you should contact the delivery person immediately to discuss further action. You should under no circumstances open the package - unless your neighbor asks you to do so. This can be expensive or, in the worst case, even result in a prison sentence of up to one year.