Let's Encrypt: Install certificate for Plesk Panel fails

Hello,

I'm using Plesk Onyx Version 17.5.3 Update #43 on CentOS 7.4.

I have been trying to install a Let's Encrypt certificate for the Plesk Panel, but I get the following error:

View attachment 14109

My Plesk Panel uses a subdomain URL like: https://subdomain.domain.nz (the main domain, 'domain.nz' is hosted on an entirely different server). I read something about using a subdomain for Plesk Panel being an issue in the past, but thought it was resolved?

Could it be...

Let's Encrypt: Install certificate for Plesk Panel fails