Domain example.com is fully secured by Let's Encrypt in Plesk but still shows the following warning under SSL/TLS Certificates option:
Security can be improved
#EXTSSLIT-1746 "A domain secured with a wildcard Let’s Encrypt certificate with all the options enabled (“Redirect from http to https”, “HSTS”, and so on) is no longer wrongly marked as “Security can be improved”."
- SSL It! 1.10.0 14 March 2022
If update is not possible for some reason you may try the following
This is a cosmetic warning bug, it can be safely ignored.