I’d not remove the .platformio\.cache folder, if you want to regenerate the project files for intellisense you have to execute the “Rebuild Intellisense” index task (Redirecting...) .
This regenerates the .vscode\* files in the project, most importantly the c_cpp_properties.json.
If there are still errors after that you’d need to show the content of that file and the path of the files you want to include.