Issue Subdomain is not secure with Let's Encrypt

[WhiteTiger]

Server operating system version

Ubuntu 22.04.2 LTS

Plesk version and microupdate number

18.0.52 Update #3

If when creating the Let's Encrypt certificate I assigned the Wildcard SSL/TLS certificate *.domain.tld, why is the subdomain (created after) still considered unsafe?
Should a new certificate be created for the subdomain?

 

[Peter Debik]

The wildcard certificate is applied to the domain, and if subdomains that are not configured are requested, it works for such subdomains. It does not work for subdomains that have an extra web server configuration by default. However, can you select the wildcard certificate from the SSL/TSL certificate selector drop down in "Hosting Settings" of the Subdomain? If not, the subdomain needs its own certificate. In my opinion that is a much better choice anyway.