The plugin works when running starting nvim, provided you specify the file name.
Running the command

nvim test.txt

makes the plugin work as expected.
However, when running

nvim

by itself, the plugin doesn't initiate.
I have the plugin config set in ~/.config/nvim/init.vim

Running

:HardTimeOn

when in nvim enables the plugin. But it still doesn't enable itself on startup without a file name specified.

let g:hardtime_default_on = 1

is of course set