Clang doesn't auto-update completion index

Don’t know how I managed to break it, but Clang now doesn’t auto update completion index, i.e. on platformio.ini file being saved.
How can I troubleshoot/diagnose it?

Could try to restart Atom?

Restarting Atom doesn’t help.

Please switch to PlatformIO IDE for VSCode, it does not depend on Clang and we provide better integration than for Atom. We will ask our users to switch to VSCode.