Hi Radek,
Replacing the earpiece speaker on your phone is a bigger job than it would seem at first glance, having to pull the motherboard to get to it. Because of that, there are a lot of connectors that had to be removed and even I've been guilty of not getting them back in place all the time.
So my suggestion at this point is that you should probably go back through the whole procedure again, and this time be very careful to make sure all of the FPC connectors are plugged in and fully engaged; my bet is you're going to find one that isn't when you check them.
Good luck; let us know what you find!