Send an argument with a pointer to an objects member function?

Question

I'm trying to make a class that queue's up functions to run after a certain amount of time has passed. The class will take a pointer of an address, a pointer to the object of that member function, and also allow up to (currently) a single parameter.

The code that errors:

cfs.taskManager.addTask(500, &GameState::print, cfs.getCurrentState(), temp);
//500: (int) time in ms converted later.
//&GameState::print: void GameState::print(std::string), takes a string argument.
// cfs.getCurrentState(): returns pointer to print object.
//temp: std::string

TaskManager.hpp:

class TaskManager
{
public:
    TaskManager();
    ~TaskManager();

    // float ms: time in milliseconds before event occurs.
    // void(C::*f)(): direct pointer to function.
    // C* o: direct pointer to object that the function is attached onto.
    // A a: Data type copy of spare argument.
    template <typename C, typename A>
    void addTask(int ms, void(C::*func)(A), C* o, A a);



    //  Dump all queued tasks.
    void clearTasks();
    //  Check if program time has passed currTime+delay of the 
    void run();

    std::vector<Task> task;
    sf::Time time;
};

This line here from above

void addTask(int ms, void(C::*func)(A), C* o, A a);

I'm led to believe that trying to pass an argument into the function pointer is the issue. I tried to make void(C::*func)(A) expect the same type of data as last parameter. When I remove template A and stop trying to pass an argument, I get no compilation errors.

Here's the compilation error I get:

error LNK2001: unresolved external symbol "public: void __thiscall TaskManager::addTask<class GameState,class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > >(int,void (__thiscall GameState::*)(class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >),class GameState *,class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >)" (??$addTask@VGameState@@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@TaskManager@@QAEXHP8GameState@@AEXV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@ZPAV1@0@Z)1  >C:\Users\Honor\documents\visual studio 2015\Projects\CFS\Release\CFS.exe : fatal error LNK1120: 1 unresolved externals

Any help at all would be very appreciated!

Edit: If I'm leaving out any crucial information, let me know I'll update really fast.