Autocomplete-clang not working

New to Atom.

I have installed autocomplete-clang but it doesn’t seem to be working. The docs say that it requires autocomplete-plus and clang, both of which I have installed.

Specifically, I am typing in the name of a structure and ‘.’ and expecting to see a list of members. This is not happening.

Is there something I am missing? Thanks-

Does it work with PlatformIO IDE for VSCode?