The same is being observed here. Plesk 18.0.61 #6, domain certs can generally be issued and renewed, but we are seeing a small number of domains where all the sudden the same error messages appears on renewal or issue attempts. I've already tried to reconfigure the domain configuration files, remove the existing certificate including removing it from the SSL directory and SQLite database (notifications ...), checked the syntax and logic of the webserver config files manually, checked accessibility of the local directories such as the acme-challenge directory, verified that Let's Encrypt acme-v02.api.letsencrypt.org can be reached and responds with expected data. All checks out good, quite unlikely that it is a local server related issue.
We got the first user complaint on July 9, 8:14 am CEST.
I actually saw something similar with cloudflare very recently where the endpoints answering apparently hadn't been provisioned with the required certificates (ironically).
Where it could possibly get worse is if cloudflares provisioners is trying to use Let's Encrypt to issue a certificate for Let's Encrypt.
I eventually added a retry mechanism and now ansible successfully got the LE's cert.
This might be a good workaround as the connection is just intermittent, sometimes out of 5 times, it only fails once.
We still have the issue right now.
None of the new certs or renews can be installed. Same error like the author posted.
We are using Plesk Obsidian 18.0.61 and CloudFlare.