Okay, thank you, my domain name is nombritech.pl and I have only tomcat there with my app placed in the root folder and some other apps also in their separate contexts.
I had a certificate earlier but it expired, I do not know how I managed to do this last time, since then I changed something in tomcat connectors, maybe that could be an issue. I thought that maybe something is wrong and deleted the old certificate, but it didn’t help.
I would like to have the certificate that is valid for www.nombritech.pl and nombritech.pl because last time I managed to do this only without the host name (nombritech.pl).
EDIT: Once I managed to do it today but it turned out that the certificate is self-signed! I was following one of the tutorials here on forum: Configuring Let's Encrypt with Tomcat 6.x and 7.x