The certificate manager and how it all ties into sysadmin is not intuitive at all imo. In certificate manager you need to check the checkbox to make the certificate the default. Then in sysadmin you need to go to HTTPS Setup > Certificate manager > select the certificate > Install.
Perhaps you already know this but you didn’t mention any of those steps so I am not sure if you did this or not.
When all else fails you can try disable the module, then fwconsole ma downloadinstall modulename and then re-enable the module again. Starting with sysadmin and then maybe try zulu. I have had to do stuff like that on occasion to get things working again.
I have used the Certificate Manager to issue a new certificate and I can see it’s assigned.
I have installed it from HTTPs and it’s installed and showing me the new validation to the domain.