Solved
IntelliSense MSVC suddenly now working
I am using TouchGFX 4.17.0 and usually I open both the TouchGFX Designer and the MSVC .sln simulator project. In the beginning the IntelliSense worked. But after a while after doing some editing work on the TouchGFX Designer, the Inteli Sense not working anymore.
So far I resolve this by crearting new project again from the Designer and 'Import GUI' and IntelliSense work again. But this is quite annoying.
As a clue, I never encounter this on version 4.16
