the plugin wont load on my 1.20 purpur server

[Yosoti]

[20:12:49 ERROR]: [ModernPluginLoadingStrategy] Could not load plugin 'Blackjack-2.4.jar' in folder 'plugins'
org.bukkit.plugin.InvalidPluginException: Unsupported API version 1.21

im on a 1.20 purpur server