Autocomplete isn't working on all the files VSCode(Ubuntu)

In my VSCode the autocomplete suddenly stopped working for some of my .cpp files. It also stopped showing those squiggly lines when there are errors present.
It works for some of my files. I assumed it stopped working for my large files but it doesn’t work on some of my small files also.

I rebuilt the C++ Intellisense index several times but to no avail. This is my c_cpp_properties file if it helps:

Thank you