Nevermind. Had to explicitly call :UpdateRemotePlugins with nvim.
Any idea why this had to be explicitly called and did not just run on its own?

The idea behind UpdateRemotePlugins: https://neovim.io/doc/user/remote_plugin.html

But I think that the error message should be improved. We can make :Semshi as a pure vim command defined in plugin/semshi.vim and dispatch to actual rplugin commands, giving a warning/error message if these commands do not exist.

The idea behind UpdateRemotePlugins: https://neovim.io/doc/user/remote_plugin.html

Actually, my question had more to do with why I had to explicitly call that function even though my .vimrc contained the following:

Plug 'numirias/semshi', {'do': ':UpdateRemotePlugins'}

I thought that "do" statement would have handled it. Why not?

I ran UpdateRematePluggins and I still have this problem.

I thought that "do" statement would have handled it. Why not?

@holmescharles
I have the same question too. After searching some related issue, I found it seems other plugins using :UpdateRemotePlugins also have similar problems when using vim-plug.

You can check this: wilder.nvim - UpdateRemotePlugins needs to be run manually. Looks like it is because the post hook of :PlugInstall(vim-plug) does not register plugins when calling :UpdateRemotePlugins .