Fake LE Intermediate X1

Jan 31, 2014
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Fresh installed Proxmox 5.2.

I did not notice the GUI had button for Certificates, so followed Let's Encrypt instructions in the wiki:
https://pve.proxmox.com/wiki/Certificate_Management
Seems I managed to create certificate first with the staging server, and now I can not figure out how to change that. Resulting in:
Fake LE Intermediate X1
in Google Chrome browser, despite refresh and relogin. And the tool claimed pveproxy got restarted.
So browser does not accept the certificate as safe.
How to get a better certificate? I think I need to force LE to stop using that staging server, but how?