Error: "Configure your Intellisense settings to help find missing headers" (was: Arduino extension required?)

something else i spotted and do not know it’s importance when going through the C/C++ debug output are these items

the key thing to verify is that you are seeing:

Custom configuration provider 'particle-vscode-core' registered
Custom configurations received:

followed by a JSON configuration block (example)

if you are still seeing issues, do you mind following the steps over here and sharing what you find there?