The following Let`s Encrypt certificates have been renewed without some of their Subject Alternative Names:
Legend:
[+] This domain is secure. The domain's SSL/TLS certificate from Lets Encrypt has been issued/renewed. [-] This domain is not secure. Either the domain's SSL/TLS certificate from Lets Encrypt could not be issued/renewed or the domain name was excluded from the certificate. Renew the certificate manually or request a new one to secure this domain
Is that your real domain name? Because it is a valid domain name that is owned by someone. But, that domain does not have any AAAA records in the DNS for IPv6 and yet an IPv6 address showed in the error. If it is not yours please do not use other people's names.
Use example.com (or example.gr) if you must although we usually need the actual name to provide assistance as the form you were shown stated.
In this case though I would suggest talking with your Plesk provider. The problem is almost certainly a configuration problem between that and your DNS. From that IPv6 address it looks like you have the domain name proxied at Cloudflare. Coordinating Cloudflare's CDN with Plesk is a question for them.