Eclipse C++ "not resolved" error

I’m trying to create a command based robot. A very simple one just for testing. I’m following a tutorial where the guy doesn’t get any of my errors
When I go and make a joystick in the OI, that is fine.

OI.h:
https://drive.google.com/open?id=1FAHxVPZ0-FUe2kP_T3c2_sIzHHU0r2nR

OI.cpp:
https://drive.google.com/open?id=1lOH7zKD-wkxw8NgSf1e7EXyMjVaIvrBF

but then when I go and do anything else like creating my chassis nothing is “resolved” or declared(that what it says if you hover over the red stuff)
I know what declared is but you can clearly tell I declared…

Chassis.h:
https://drive.google.com/open?id=1qLWqOVI-bYoIwzgTY3sNaS1wqGCsxDog

Chassis.cpp:
https://drive.google.com/open?id=1LgVYZed9BtnzSt_FyTb0-2HgAdPdE3H1

I have downloaded and re-downloaded. Rebuilt indexes and everything in between. What I find weird is that is worked in the OI but not the rest.

Please Help, anything helps!!

Take a look at the #includes in your working example vs. chassis.h