How can I fix broken https on Cockpit?

I've just installed cockpit on my CentOS 8 box: dnf install cockpit systemctl start cockpit.socket systemctl enable cockpit.socket Once I'd let it through the firewall, I can get it up on a.b.c.d:9090 in my browser. But Chrome is saying Not secure, with https crossed out in the address bar. When I click on the warning and then Certiciate (invalid) it tells me Windows does not have enough information to verify this certificate. It says the certificate was issued by myhostname, to myhostname, and that it's valid from today until 2031. If I go to Certification path then Certificate status it says The issuer of this certificate could not be found.` I'm unclear whether my connection IS encrypted or not. Is Chrome just saying it doesn't like the certificate, or is it actively not using it and forcing http? I've checked the guide at https://cockpit-project.org/guide/latest/https.html and running remotectl certificate I can confirm that the file is there and is apparently being used. How can I fix this? Thank you!