Arduino Mini and WiFi shield -> not present (status 255)

I have an issue with the WiFi shield. As you can see in the picture below, I am experimenting with the Arduino Mini and the WiFi shield.

I have read the tutorial-guide and connected all the necessary pins between the Mini and the shield. I use the example code which is provided in the tutorial, e.g. reading the WiFi shield's MAC-address or scanning for networks near me.

But anything I get is the error message, that the shield is not connected. But there is a connection between the two Pin 7's (the handshake pins) and even to any other required pin. I even support my circuit with an additional power supply of 5V (the voltage regulator in the picture), so what's wrong with it? Or might it be that the WiFi shield itself is damaged or has a malfunction? How to verify this?

One last question is: Do they deliver the shield with an installed firmware or does the user have to install it?

The code I use is for example:

uint8_t wl_status = 0;

void setup()
{ // code to run once 
  // Open serial communications
  Serial.begin(115200);
  Serial.println("*** Arduino board online ***");
  
  // check for the presence of the shield:
  wl_status = WiFi.status();
  if (wl_status == WL_NO_SHIELD)
  {
    Serial.println("-E- WiFi shield not present"); 
    // don't continue:
    //while(true);
  }
  else
  { // Initialize Wifi
    Serial.println("-I- Initializing Wifi..");
    printAddress(1);

    // Scan for existing networks:
    Serial.println("-I- Scanning available networks..");
    listNetworks();
  }

  Serial.print("-D- Wifistatus : ");
  Serial.print(wl_status, DEC);
  Serial.println("");
}

The printAddress()-function simply prints out the MAC-address of the shield.

I proved whether a different power source will work or not; the problem still remained.

Arduino support suggested that we should use the SPI connection of the board instead of wiring. It was worth a try, so I combined the WiFi-shield with an Arduino Uno and could finally start practising. Forget the Arduino Mini and use Uno or Mega instead.

According to the startup trouble, the current firmware version still has bugs, e.g. connection dies after a few seconds both on server side and client side. I recommend checking the Git repository frequently for updates. Issue #9 (Connection dies after a few seconds) has been solved on server side only, however the problem still exists on client side. I will wait for the next version of the firmware.