This sounds like my problem. My certificates work on my new Macbook Air and on iPhone, but not on my old iMac 24 inch with El Capitan.
I have a windows 2012 R server and I used win.acme when I updated the certificates.
The problem address is atervinnmera.se and manmade.se
I don´t know where I can find the cert.pem file so I can change it to fullchain.pem? Thanks.