MineChess was fully remade from scratch, it's like a completely new plugin with several improvements and fixes. If you want to continue using this plugin, before updating (if you have been using the plugin before) you need to delete the whole MineChess folder. You will lose your player data and configuration, yes, but sadly this is the only way to update to the new version, because the amount of changes were so big that it was impossible for me to create a type of migration system.
All features of the old versions of MineChess are available in this new version, but now there is a
PAID version that includes new features such as player vs computer, 3d models for pieces, and more.
There is also a new WIKI:
ajneb97.gitbook.io/minechess
Creating the plugin again from scratch will allow me to fix bugs and make updates in a more easier way than before, so I hope you understand this! Let me know in the discussion if you need any help and remember to check the wiki!