When starting Plesk autoinstaller to upgrade Plesk in Home > Tools & Settings > Updates and Upgrades the option Install or Upgrade Product is greyed out. Why?
Option Notify me when the upgrade to the following Panel release tier is available set as (Recommended) General release in Home > Tools & Settings > Update and Upgrade Settings:
CONFIG_TEXT: A general release has passed all quality tests. Minor issues are promptly fixed by updates. We recommend that you always upgrade Panel to general release versions.
So the new Plesk versions that are not matching to General release tier requirements cannot be upgrade from Update and Upgrade.
In order to install a new Plesk version under set option Notify me when the upgrade to the following Panel release tier is available as Early adopter release:
Use knowledge base article for more detailed information regarding Plesk Release Tiers