VSCode:1.65.2 OS: Ubuntu 20.04

When I try to compile my C++ code in VSCode terminal or system terminal, I get an error message saying

fatal error: 'itensor/all.h' file not found

Then, I updated include path settings in VSCode to add paths to required header files because I get squiggles under header files saying

include errors detected, update include path settings.

Yet, my build task fails and header files are not being read.

Kindly help.

I referred some previous answers, but they don't seem to work for me at all.