How to make a website hosted in Plesk use a secure connection over HTTPS permanently?
Before enabling permanent HTTPS redirection for a domain, make sure that the website is accessible over HTTPS:
The setting SSL/TLS support is enabled in Hosting Settings of a domain.
Go to Domains > example.com > Hosting Settings.
Enable the setting Permanent SEO-safe 301 redirect from HTTP to HTTPS and select your certificate from the drop-down menu. Apply the changes.
Note: If the setting Permanent SEO-safe 301 redirect from HTTP to HTTPS is grayed out, please contact your service provider for assistance with permanent HTTPS redirection.
Alternative solutions for Linux
Alternative solutions for Windows Server