The plugin will not work until absolutely all the actions specified on the wiki. Didn't specify a key - will bungee crash. Do the server names in the JPremium config not match those in the Bungee config? - There will be a crash. And that's the way it is in everything.
After full configuration, the plugin works fine.
5.3.2 - not working, waiting for update / download 5.3.1.
P.S. Translated through Deepl.