Why does compiler say it can't see a template it has just generated?

If you look at the following (edited) compiler output (Visual C++ 2013) you will see that on line 5 it tells me it is compiling (I use an explicit instantiation in a precompiled header):

TimeOnly IT_TimeOnly::operator ++<TimeOnly>(int). 

This is the templated postfix operator for IT_TimeOnly class. However, on line 7 the compiler warns that a postfix operator for type IT_TimeOnly cannot be found. Can anyone help me understand why? My code is shown below.

1>------ Build started: Project: TemplatedPostFix, Configuration: Debug Win32 ------
2>  stdafx.cpp
3>  Precompiled Header
4>c:...\it_timeonly.h(14): warning C4305: 'initializing' : truncation from 'int' to 'bool'
5> c:... \to_timeonly.h(22) : see reference to function template instantiation 'TimeOnly IT_TimeOnly::operator ++<TimeOnly>(int)' being compiled
6> Test_TemplatedPostFix.cpp
7>c:...\test_templatedpostfix.cpp(31): warning C4620: no postfix form of 'operator ++' found for type 'IT_TimeOnly', using prefix form

My Interface class with templated postfix:

typedef signed char period_t;

class IT_TimeOnly
{
public:
    template<class T>
    T operator++(int) {
        bool b = 2;  // here to generate warning for debugging
        std::cout << "Template Post++\n"; 
        return static_cast<T*>(this)->operator++(1); 
    }
    virtual IT_TimeOnly & operator++() = 0;
    virtual period_t getMins() const = 0;
    virtual void setMins(period_t) = 0;
};

My concrete derived class:

class TimeOnly : public IT_TimeOnly
{
public:
    TimeOnly(){};
    TimeOnly(const IT_TimeOnly &);
    TimeOnly(const TimeOnly &);
    TimeOnly operator++(int);
    TimeOnly & operator++() override  {
        cout << "Derived Pre++\n";
        ++mins;
        return *this;
    }
    period_t getMins() const override;
    void setMins(period_t mins) override;
private:
    period_t hrs = 0;
    period_t mins = 0;
};

I have explicitly instantiated the template for TimeOnly in my pre-compiled header. That produces lines 3, 4 and 5.

template TimeOnly IT_TimeOnly::operator++<TimeOnly>(int);

And my test code:

IT_TimeOnly & myBaseTime = myTime; // Base-class reference
myBaseTime++;
cout << (int)myBaseTime.getMins() << '\n';

// Prints: 
// Derived Pre++
// 1