A new Plesk version is released for early adopters. It is not possible to upgrade Plesk at Home > Tools & Settings > Updates and Upgrades as the option Install or Upgrade Product is greyed out.
Plesk upgrade is configured as (Recommended) General release in Home > Tools & Settings > Update and Upgrade Settings.
The new Plesk versions that are not matching to General release tier requirements are not available in Update and Upgrade.
For more detailed information can be found in the article:
To be able to upgrade to a new Plesk version for early adopters log in to Plesk as admin user, tick the option Early adopter release and click Ok at Home > Tools & Settings > Update and Upgrade Settings: