I would like to ask you to update the plugin TardisChunkGenerator. The one in the search list is for minecraft v.1.12 and it does not work with the official TARDIS plugin (1.16.3). The author does not update this plugin on dev.bukkit.org anymore.
The latest version can be found here http://tardisjenkins.duckdns.o…job/TARDISChunkGenerator/
I have read that Aternos requires everything to be distributed on official sites (such as dev.bukkit.org and spigotmc.org) and this plugin is. Just it is put with the main TARDIS plugin into archive, so it is not in the list. This is the reason why this plugin is outdated.
And, as I know, TardisChunkGenerator is required to be updated with every new Minecraft update, so please consider updating it again in the future.