HTTP website loads fine but while trying to load the same website with HTTPS, it loads Plesk default page.
Incorrect vhosts structure of the domain.
Connect to the server via SSH;
Repair the vhosts structure by executing the following command:
# /usr/local/psa/bin/domain --update example.com -same_ssl true
SUCCESS: Update of domain 'example.com' completed.
If the issue persists, run the following command:
# plesk repair web example.com