Static cast with derived keyword (Code understanding) [duplicate]

I was trying to compile c++ code got from internet, unfortunately it is not failed to compile. Since it is heavily templeted code I am struggling to understand and fixing this. The code is giving below.

template<typename Derived, typename... Elements>
class ElementVectorBaseNew {
private:
   typedef std::tuple<Elements...> Tuple;

public:
   static const int kN = sizeof...(Elements);
   //static const bool kIsVectorSpace = CheckAllTrue<Elements::kIsVectorSpace...>::kVal;

   template<int I, int C = 0, typename std::enable_if<(std::tuple_element<C, Tuple>::type::kI == I)>::type * = nullptr>
   static constexpr int GetC() {
       return C;
   }

   template<int I, int C = 0, typename std::enable_if<((std::tuple_element<C, Tuple>::type::kI !=
                                                        I))>::type * = nullptr>
   static constexpr int GetC() {
       static_assert(C < kN - 1, "Index not found in ElementVector");
       return GetC<I, C + 1>();
   }

   template<int I>
   typename std::tuple_element<GetC<I>(), Tuple>::type::Type &Get() {
       return static_cast<Derived &>(*this).Get<I>();
   }
};

Getting following error

In member function ‘typename std::tuple_element<GetC<I>(), std::tuple<_Elements ...> >::type::Type& ElementVectorBaseNew<Derived, Elements>::Get()’:
/home/elan/Dev/state_est/externel/two_state_information_filter/include/tsif/element_vector_new.h:33:53: error: expected primary-expression before ‘)’ token
   33 |         return static_cast<Derived &>(*this).Get<I>();

I am using gcc 9 for compiling. Can anybody have a look and give more information of what is wrong with this code.