Okay this one had me a little bit worried, after I fixed the define file, it was still throwing up the error:
The Fix:
1.) close visual code + unreal
2.) go to the directory where your projects are mine: C:\Users\Drago\Documents\Unreal Projects\ToonTanks go into your binary file and delete anything inside that folder
3.) Reload unreal it will ask you to build, build it, then rebuild visual code, include your defines again and hey presto its working 
I thought this might help some people if they’re having the same error.