DLL injection (Failed to inject)

I have found this complete and easy example to test the function hook:

https://github.com/Zer0Mem0ry/Detour

#include <Windows.h>
#include <iostream>

#include "detours.h"
#include "sigscan.h"

// this is the function that the program
// will jump to when sum() is called in the original program (testprogram.exe)

DWORD AddressOfSum = 0;
// template for the original function
typedef int(*sum)(int x, int y); 

int HookSum(int x, int y)
{
    // manipulate the arguments
    x += 500;
    y += 500;

    // we manipulate the arguments here and then
    // redirect the program to the original function

    std::cout << "your program has been hacked! " << std::endl;
    sum originalSum = (sum)AddressOfSum;
    return originalSum(x, y);
}

BOOL WINAPI DllMain(HMODULE hModule, DWORD dwReason, LPVOID lpReserved)
{
    // store the address of sum() in testprogram.exe here.

    if (dwReason == DLL_PROCESS_ATTACH)
    {
        // We will use signature scanning to find the function that we want to hook
        // we will find the function in IDA pro and create a signature from it:

        SigScan Scanner;

        // testprogram.exe is the name of the main module in our target process
        AddressOfSum = Scanner.FindPattern("testprogram.exe", "x55x8BxECx8Bx45x08x03x45x0C", "xxxxxxxxx");

        DetourTransactionBegin();
        DetourUpdateThread(GetCurrentThread());

        // this will hook the function
        DetourAttach(&(LPVOID&)AddressOfSum, &HookSum);

        DetourTransactionCommit();
    }
    else if (dwReason == DLL_PROCESS_DETACH)
    {
        // unhook
        DetourTransactionBegin();
        DetourUpdateThread(GetCurrentThread());

        // this will hook the function
        DetourDetach(&(LPVOID&)AddressOfSum, &HookSum);

        DetourTransactionCommit();
    }
    return TRUE;
}

I have tried to inject this DLL to the "testprogram.exe" (without change nothing) using cheat engine, extreme inject, etc.. with the some result "failed to inject".

I need to change "xxxxxxxxx" before inject the DLL ?

Can you help me please ?

Best Regards