How to pass const char* as parameter of LPCSTR parameter?

I want to use this function to call the PlaySoundA function, but the sound file I want to play doesn't open.

void AudioClass::playAudio(const char* incomingData, const char* filePath)
{

    char buffer[100]; // <- danger, only storage for 100 characters.
    strncpy_s(buffer, filePath, sizeof(buffer));
    strncat_s(buffer, incomingData, sizeof(buffer));

    PlaySoundA(buffer, NULL, SND_FILENAME);
}

As I found out, if the argument to the LPCSTR pszSound parameter of PlaySoundA() is given as a string (eg "C:/Users/User/Documents/sound.wav"), i.e. the full path to the file is given, the sound will play.

I want to combine incoming data parameter (filename) and filePath parameter, for this I use buffer.

If the file is not found, the default system sound (beep in my case) should play, but this is no longer the case. Even if the SND_NODEFAULT flag is not set, PlaySoundA() will return silently in this case without playing the default system sound.

https://docs.microsoft.com/zh-cn/previous-versions/dd743680(v%3Dvs.85）

Is it possible that the parameter I am trying to pass is not compatible with the LPCSTR pszSound parameter?

When running the debugger, the buffer variable seems to hold the entire path (C:/Users/User/Documents/sound.wav\r\n), but why is there a \r\n prefix at the end?

definition:

#define MAX_DATA_LENGTH 255

char incomingData[MAX_DATA_LENGTH];

const char* filePath {"C:/Users/User/Desktop/"};

//Arduino SerialPort object
SerialPort *arduino;

//Audio file AudioClass object
AudioClass* audio;

Call playAudio() here:

void exampleReceiveData(void)
{
    int readResult = arduino->SerialPort::readSerialPort(incomingData, MAX_DATA_LENGTH);

    audio->AudioClass::playAudio(incomingData, filePath);

    Sleep(10000);
}

EDIT_1: The real file path I'm using is less than 100 characters long.

EDIT_2: I get this warning: String 'buffer' may not be zero-terminated.