What would I like to be done?
I need someone to help me to get a grade of A+ on my SSL and fix the error I get via feedvalidator. I guess when the SSL is fixed, this will automatically will be fixed too since it is a SSL problem.
You’re missing the intermediate CA certificate. The SSL labs report shows what cert you’re missing. Find it (Certum should have sent it to you with the end entity certificate) and paste it in the same file as the end entity certificate, immediately after it in the file. Restart nginx (or the whole container, if you’re feeling brutal) and everything should start working.
You’d be better off posting that as a separate topic, with its own, more descriptive, title. I can see what’s going on, I’m just not sure how best to fix it, so it’ll be best if someone with more knowledge in that space chimes in.