It seems the plugin download link on spigotmc.org is hacked or something. It opens a page with pop-ups that re-opens itself to fill the location history and doesn't seem to lead anywhere to download.

Hey! Please use the CurseForge page instead! https://dev.bukkit.org/projects/chests-plus-plus

The spigot page is now back up too https://www.spigotmc.org/resources/chests-chest-linking-hopper-filtering-remote-chests-menus.71355/