Hello everyone! While looking for the answer for my issue on the Internet, I've found this site and truth be told feel very happy about it because here you guys are trying to resolve the same problems I have at the moment. Please sorry for English here, unfortunately I don't know Polish, but nevertheless have a hope that someone could help me with my problem.
On the http://www.mf.gov.pl/kontrola-skarbowa/dzialalnosc/jednolity-plik-kontrolny/-/asset_publisher/2NoO/content/specyfikacja-interfejsow-uslug-jednolitego-pliku-kontrolnego# website I've foundPokaż całość

Hello, guys! Production environment doesn't work for me. Does anybody have the same problem? Thanks

@mmm234: thanks for you support very much! I converted .cer to .crt and it should work now. Previously I was a little bit confused as initially they provided .crt file and then, for prod. env., they gave a .cer file. Thanks very much!