Why are functions from an included file showing an error for undefined references?

I'm using TrueStudio and I am getting an error on functions from another file. The file is in the Inc folder, is included in the project settings Path and Symbols, and my main has the #include (filename) at the top. Also, whenever I ctrl click on the functions, it takes me to the correct file, so it does know where the functions are defined. I'm new to this, but from what I researched the functions should be recognized. Thanks in advance!