This is not a drop-in replacement! See https://github.com/ServerSelectorX/ServerSelectorX/wiki/Premium-|-Installation-Instructions

New version of ServerSelectorX. This version is made for 1.13 and 1.14 only and probably will not work on older versions. The old version is still included in the zip, and is still supported. Changes:
- Completely redesigned the layout of menu files, making the plugin easier to configure. The config file is much shorter now.
- Added a configuration synchronization feature. This allows you to automatically sync menus and other configuration files across servers, so you don't have to manually copy files to all servers after making changes.
- General performance improvements and bug fixes
- Allow the use of 1.13 and 1.14 item names

Please note that this is a release candidate and is not guaranteed to be stable. Additionally, not all wiki articles have been updated yet.