Well, I dont know where your problem is from. So I can also suggest what I would try.
- delete the {ProjectName}_Data folder. That stuff is all rebuilt.
- check if the code completion does not work at all, or just not for your case.
When you add a simple test.c with its own struct definition and use of it, does it work there? Maybe the language parser is confused by some constructs in your code or does not get the preprocessor defines right.
Well, I'm only guessing around, sorry.
Daniel