The old file was over a mb, which i found odd, but it's compiled correctly now, and is about 6 kb. Also before when leaving the leave-message empty in the config, it wouldn't send the default leave message.

I have only tested 1.16.5 and 1.17.1, but the plugin should work on servers from 1.17 to 1.13, let me know if it does or doesn't.