Unresolved external symbol C++, Simple Issue

Question

I am having this issue when compiling C++ in Visual Studio 2022:

Error   LNK2019 unresolved external symbol "public: __cdecl QueueInterface<char>::QueueInterface<char>(int)" (??0?$QueueInterface@D@@QEAA@H@Z) referenced in function "bool __cdecl isPalindrome(class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >)"...

I have developed in Java for years, but I clearly don't understand the basics of C++ to solve what I assume is a simple issue. I have commented out the code and determined that the way I am constructing this QueueInterface class is not right. I would greatly appreciate any assistance to help me understand what I am missing.

The main() is below:

#include <iostream>
#include <string>

#include "QueueInterface.h"

using namespace std;

int main()
{
    QueueInterface<char> aQueue(25);

}

The header file:

#pragma once

#ifndef QUEUE_INTERFACE_
#define QUEUE_INTERFACE_

using namespace std;

template<class ItemType>
class QueueInterface
{
public:
    /* Not sure why the book left out the constructor. Not sure how this would be possible otherwise */
    QueueInterface(int length);

    /** Sees whether this queue is empty.
     @return  True if the queue is empty, or false if not. */
     bool isEmpty();

    /** Adds a new entry to the back of this queue.
     @post  If the operation was successful, newEntry is at the
        back of the queue.
     @param newEntry  The object to be added as a new entry.
     @return  True if the addition is successful or false if not. */
     bool enqueue(const ItemType& newEntry);

    /** Removes the front of this queue.
     @post  If the operation was successful, the front of the queue
        has been removed.
     @return  True if the removal is successful or false if not. */
     bool dequeue();

    /** Returns the front of this queue.
     @pre  The queue is not empty.
    @post  The front of the queue has been returned, and the
       queue is unchanged.
     @return  The front of the queue. */
     ItemType peekFront() ;

    /** Destroys this queue and frees its memory. */
    virtual ~QueueInterface() { }

private:
    ItemType* queue;
    int size;
    int length;
}; // end QueueInterface
#endif

The implementing file:

#include <iostream>
#include "QueueInterface.h"

using namespace std;

template<class ItemType>
QueueInterface<ItemType>::QueueInterface(int thisLength) : length(thisLength), size(0) {
    queue = new ItemType[length];
}

template<class ItemType>
bool QueueInterface<ItemType>::isEmpty()  {
    return size == 0;
}

template<class ItemType>
bool QueueInterface<ItemType>::enqueue(const ItemType& newEntry) {
    if (size == length - 1) {
        return false;
    }

    queue[size] = newEntry;
    size++;
    return true;
}

template<class ItemType>
bool QueueInterface<ItemType>::dequeue() {
    for (int i = 1; i <= length; i++) {
        if (i == length) {
            queue[i - 1] = NULL;
        }
        else {
            queue[i - 1] = queue[i];
        }
    }

    size--;
    return true;
}

template<class ItemType>
ItemType QueueInterface<ItemType>::peekFront()  {
    return queue[0];
}