When creating a new subscription or domain at Subscriptions > Add Subscription "Registered domain name" field suggests to enter
www.domain.name instead of
This results that http://domain.name shows:
Plesk Web Server's Default Page
#PPPM-12883 "Improved a hint for creating temporary domains. The previous hint was incorrect and could mislead users into specifying a temporary domain name that did not work."
- Plesk Obsidian 20 April 2021
If update is not possible for some reason you may try the following