Eclipse 20.1 Failures with #include

Before I begin, I have all my Eclipse settings "correct" for inclusion of files. I do have a project working in Eclipse 20.1

However, upon refactoring functions from main to other files, the basic #include directive in C is not working consistently.

It works for some files, but not for others. I'm running Windows 10 Pro Build 19043 and Quartus 20.1 Prime Pro Standard edition with Eclipse 20.1

For example, function "void general_function()" was placed in general.h and general.c

In my main file, when I include with

#include "general.h"

I get the message of "undefined reference to general_function()"

However, other include files to work. If it failed for all of them (and they are all in the same root directory), I would think it would be my fault for the way that I organized the files or did not setup Eclipse properly. However, with inconsistent includes, this is quite problematic for having any real confidence in Eclipse 20.1

Any suggestions are greatly appreciated. Thanks. James