getaddrinfo returns previous fixed IP address

Question

Context: My C++ application needs to know on which computer it is running in order to do specific behavior. So my application gets the IP address of the computer and then check that address in a configuration file with an IP list in order to determine the computer's role. All computers have a fixed IP address. I am using gethostname, getaddrinfo and inet_ntop in order to do that.

Problem: On some target platform's computers, getaddrinfo returns the old IP address (the address before I set the fixed value). But if I am doing "ipconfig" in the cmd, the expected fixed value is shown. It is also pingable by other computers. All computers have only 1 network card, IPv6 is disabled.

Platform: Windows 7 x64.

IDE: Visual Studio 2015.

I would like to have the actual fixed IP address. Thank you for your help!

Code sample:

// [Some stuff...]

addrinfo hints;
addrinfo *pResults;
int returnedCode;
char hostName[1024];

if (0 != (returnedCode = gethostname(hostName, sizeof hostName)))
{
    // Error handling stuff.
}

memset(&hints, 0, sizeof hints);
hints.ai_family = AF_INET;     // Only want IPv4.
hints.ai_socktype = SOCK_DGRAM; // UDP stream sockets.
hints.ai_flags = AI_PASSIVE; // Fill in my IP for me.

if (0 != (returnedCode = getaddrinfo(hostName, NULL, &hints, &pResults)))
{
    // Error handling.
}

struct addrinfo* res;
char buffer[INET_ADDRSTRLEN];
std::string localIP;

for (res = pResults; res != NULL; res = res->ai_next)
{
    if (res->ai_family == AF_INET)
    {
        const char* ip = inet_ntop(AF_INET, 
               &((struct sockaddr_in *)res->ai_addr)->sin_addr, buffer, INET_ADDRSTRLEN);

        if ((NULL == ip) || (nullptr == ip))
        {
            // Error handling.
        }
        else
        {
            localIP = std::string(ip);
        }
    }
}

freeaddrinfo(pResults); // free the linked-list
WSACleanup();
// [More stuff...]