The size of your coefficients result in a flood of error messages from NDSolve and from Plot.
If I scale those way down then I can at least demonstrate syntax that appears to work.
In:= eq=Gx+Dif n''[x]-Kr(n[x]-n0)==0;
Check all of this very carefully to make certain that this makes sense and there are no errors. Then you can try to decide what to do to blow up your coefficients again.