If it was empty and you refilled it and it is empty again, you have a leak..

Does finland have top off cans available at your parts store? it doesn't take much pressure loss for the pressure switch to kill the system. If you top it off a little more and it works, it might keep working. I had to do a second add to my system when I used a shop to fill it with the proper amount.. I topped it off about a week or two later and it worked ever since.